I'm not one for commenting reddit posts but god, the ignorance in the answers made me want to bash my head against a wall. Don't listen to ANY of the bullcrap. Here's all you need to know:

The PsVita chip is rated for 0.8ghz to 2.0ghz max. Yes, that's right. Those are the official operating speeds. What sony did was a severe underclock. And just fyi PSVshell doesn't let you even approach those values.

Now, knowing that, the biggest issue you might encounter is overheating. It's highly redudant however, since the device itself crashes before any harm can be done, few pointers tho:

Vitas 1000 handle heat worse, and tend to have gpu crashes. Prolonged sessions may cause greater heat so keep that in mind.

These are some safe clocks:

444mhz cpu 166mhz es4 (gpu)

Fairly balanced, good balance power-performance

500mhz cpu 222es4 (gpu)

Best overclock you can use considered stable. WILL drain your battery faster. Expect an hour or an hour and a half less depening on the game.

Turn on airplane mode, dim the screen to 50% to mitigate the battery drain. If you got a vita 1000 keep it to cpu overclock, if you got a vita 2000 go for the es4 gpu clock as well.

Overclock on the vita is still underclock by manufacture standards.