It's good practice not to update to something new immediately, for example when 3.55 CFW went out, I stayed on 3.41 for a while until things got stable and games stopped working on 3.41 when I decided to make the switch to CFW. Same with 4.xx, I stuck with kmeaw until things got stable and games stopped working on kmeaw (or needed patching to work if you want) when I decided to upgrade to Rebug 4.30. Same now with 4.40, I will stick with Rebug 4.30 until 4.40 becomes stable and games stop working on 4.30 when I would upgrade to Rebug 4.40 which would be released by then.

So I'm not saying everybody should update immediately when a new CFW goes out, all I'm saying is that there's little to no reason to stay on kmeaw nowadays because it's 3 generations old now considering the following:

1st generation JB: 3.41 with dongle
2nd generation JB: 3.55 CFW
3rd generation JB: 4.21 CFW
4th generation JB: 4.30 CFW
5th generation JB: 4.40 CFW

I believe you should never be older than 1 generation old (i.e. older than 4.30 CFW now)