Well, as usual, I'll lead by suggesting you take a look at destroyor's FAQ. There are some spoilers, but they're mostly tagged and forewarned, so even if you haven't finished the game, you can avoid plot details easily. Here's the link:
https://steamcommunity.com/sharedfiles/filedetails/?id=843557165Lockpicking of 100-110 with tools but without food buffs is probably as high as you're ever going to need to go. Hacking, you could make a case for taking up to 130 with food but without tools, but unless you intend to use it in that one specific way, then there's not much call to take it above 110-120.
The only skills that you realistically want to max all the time are your primary combat skills; guns, melee, crossbows, psi. And even those don't
need to be capped, it's just that the difference is noticeable when you don't keep them maxed out.
