Both the popular 8.33 12 volt solutions, Trig and Garmin have a memory facility if, like piperboy84 above, you're becoming neuronally challenged. Our Garmin 255 also has 'last 10 used' facility. Also, it has a 'monitor' facility so I can talk on one channel and listen to another, only possible with 2 boxes previously. If you want to talk on the 2nd channel, then just hit the flip-flop button instead of having to reach for the comm panel. I find this so much easier and in fact don't feel the need for our 2nd comm box. We've retained it for the 2nd ILS/VOR function and just have COM tuned to the ATIS. I'm finding new, useful, features in the Garmin all the time. The Trig has a 'last received' button, too; saves those 'say again' moments (and 'was that for us?'!)
All in all, it was an expense, but in our case, rather than making us pack up, it had a positive impact on thinking about our radio stack and how we use it.
Next up, replacing our aged mode 'C' transponder, which is sometimes reported intermittent and is a real pain to use. We're going for a nice push-button solution with ADS-B out and re-positioning it for greater convenience. But then we currently train for the IMC/IR(R) rating as well as ab initio LAPL/PPL so it's all good.
Oh, and actually, there are only 5 digits to remember, not 6. Simply train your brain to eliminate the first '1' as it's the same for all channels and in fact is redundant.
TOO