If you can retire on 4/1, do you really need the extra $5K? Once you've hit your "numbers", does extra really matter?
Um, yes. I assume this is a bonus earned for work put in, standards met, or something similar. So take it. Your "number" plus 5K is better than just your number. Totally worth another -- was it two months?
Incidentally, I intend to do something similar. I'll reach my date November 1 (not this year), but if I stay 'til the end of the semester, I'll be paid for Thanksgiving break, Christmas break, and the end-of-semester county supplement. We're talking about 10 weeks of extra work so I can pick up those benefits I've earned over the years -- I'm not going to leave earned bonuses behind.
Similarly, my sick days can be used to add years to my service /increase my pension. Every 20 days = 1 more month, and it "rounds up". So 21 days = 2 months service; however, 25 days still = 2 months service. Since sick days are an earned benefit, I'm going to make sure I don't leave with 39 days! A friend of mine who's retiring this year decided to work the rest of the year (he had been planning to retire at Christmas) because he figured out that if he stays that extra six months, the sick days he'll add will put him "over" a significant number.
Having said that, I'll add this clarification: When I'm nearing my date, I would not do anything that would add work to other people (for example, sometimes we don't have substitute teachers -- I would NOT burn through my sick days if I knew that other teachers would have to fill in for me).