What are the recommended iMac specifications for a 5-year lifespan?

As much RAM as you can afford. As much storage as you can afford. That’s about it. Software requirements continue to grow, app size and data size continue to grow. Hardware has to keep up with software, not the other way around.

I agree with our friend, @Ikrupp. 👍🏽

To put it another way, don't go with the Mac's entry level spec. Bump up the RAM (min 24 GB) and the drive capacity (min 1 TB) and you may easily use your next Mac for 7-10 years.

In addition to RAM and HDD capacities already mentioned …

… it can’t hurt to get the newest “M” processor you can afford.

This method will help keep you “current” with MacOS “upgrades” as long as possible AND still allow you to continue to productively operate even after your hardware is no longer receiving the “latest and greatest” OS “upgrades.”

Many Mac users who went “high end” at initial purchase are still productively computing on hardware now only capable of running Ventura or even older OSs.

lkrupp wrote:

As much RAM as you can afford. As much storage as you can afford. That’s about it. Software requirements continue to grow, app size and data size continue to grow. Hardware has to keep up with software, not the other way around.

With the 24" iMacs, I would also recommend getting one of the models that has four USB4 / Thunderbolt ports.

The entry-level model has only two of those ports – and there's nowhere else to plug in USB peripherals, so you will find yourself needing a hub or dock very quickly.

Chattanoogan wrote:

In addition to RAM and HDD capacities already mentioned …

… it can’t hurt to get the newest “M” processor you can afford.

There are two aspects.

• Generation: M1, M2, M3, M4, M5. M5 is the latest, but currently only available on entry-level 14" MBPs – and on iPad Pros (which don't run macOS).
• Processor level: Plain, Pro, Max, or Ultra. As you go up to higher levels, you get more GPU cores, more/faster CPU cores, the ability to order more RAM, etc. Within a level, there may sometimes be variants (e.g., you can get the 24" M4 iMac with either 8 or 10 GPU cores).

The 24" M4 iMac uses plain M4 processors. If the OP wanted a stronger GPU, the OP could get the Mac mini in versions that have M4 Pro chips, or the Mac Studio in versions that have M4 Max chips.

For everyday use (i.e., not high-end gaming, or intensive photo processing or video workloads), even the GPU in the plain M4 chip is likely to be strong enough.

Get at least the recommended specs for your important (heavier) apps, and get no less than a middling model Mac with more memory and more storage than your current usage trends.

Given your current hardware, likely options are Mac mini M4 with your own peripherals and your own 4K or 5K display, or an iMac with the one-size fits all 24” display, whatever Mac with 16 to 24 GB memory minimally, and, again, whatever fits with your current memory and storage trends.

Also check how many USB-A, USB-C, HDMI, 3.5mm audio, and/or Thunderbolt ports are needed both now, and your trend.

You’ll probably want a hard disk of two to three times the size of your internal storage for Time Machine backups, or a NAS with Time Machine server support if you have the budget and the usage requirements for that. Or you can repurpose the existing iMac as a NAS, with sufficient external storage added.

One other detail: M-class processors and Apple main storage are stupidly fast. Picking a top-spec iMac 2020 i9 ten-core, Geekbench has 1644 single-core and 8800 multi-core, while the iMac 2024 M4 low-spec 8-core is 3749 and 14076. Very nearly double the performance, and in ~four years.

MacRumours has a guide to the Apple product release cycles here: https://buyersguide.macrumors.com/#mac

PS: I am amused by the “as you can afford” recommendations here though, as that might well sell some few folks here on a fully loaded Mac Pro, and a low-spec mini for the rest of us, dear reader. And Apple has as many salable variations available as different buyers have available cash. 😉

I recommend getting a Mac Mini M4 with a 3rd party monitor. I have the following: a 10 Core Mac Mini M4 with 16 GB RAM and 1 TB SSD ($1084) with a 32" LG 4k monitor ($331) from Amazon.com)  is $1415 which is $541 less than a similarly configured new 24" iMac ($1956)  re 07/2025. Keep your keyboard and mouse from your current Mac for use with the Mini.  It leaves my previous i7 2017 17" iMac in its dust.

I got the above Mini with a 32" LG 4K monitor w/speakers for only $60 more than the 27" (didn't know the Mini had a speaker).  There are many monitors available in the 27" size for $100 on up to $500 depending on what features you want.  The monitor prices are before tariffs.

I would mention a 24" iMac has a 4.5K resolution screen, which means, it will look sharper than any 4K monitor regardless of size or price. You would need a 5K or better monitor to look as good. Of course if you have poor eyesight that may not matter.

Note that you can add external SSD storage – but you can't add external RAM.