Another thing to think about as far as using annual leave or cashing it out, is the rate at which it will be paid. I worked with a guy who had been working a "term promotion" worth about $3/hour more. He saved up his annual leave to cash it out when he retired, thinking he'd get the higher rate. When he retired, they cashed out his leave at his permanent rate, rather than the higher rate. The term promotion did help him on his high three, but he would have made more money taking that annual leave.
With sick leave, to earn a full year on your pension, you basically have to work 20 years without taking any sick leave at all. To me, that's not worth it. If the sick leave would bump me into MRA eligibility (by adding time, even if I'm not there age-wise yet), it might be a little more tempting, but it doesn't. I keep a nice bank of hours, but I have no problem calling in sick.
And can I just say it's nice to be able to discuss this with people in a similar boat? Most of the people I work with feel like they will never be able to afford being able to retire, plan to work through their 60s, and have a "good luck with that" type response when they find out I'm planning to leave the first date I'm eligible. The non-coworkers don't understand all the nuances with TSP/fed stuff. While I'm not trying to get out as early as many here, I understand that process too because I was desperate to get out of my last position, and would have taken a large hit on my retirement just to escape (fortunately it didn't come to that, but I did take a paycut for my current position, and don't regret that decision at all).