Don't think I would because she's a pain and there's usually lots of stallions at the shows we go to, not always under perfect control! Last year we had to make the decision to go back onto regumate in August as we had a big show approaching and she was virtually unrideable; this yr she's had a marble inserted so fingers crossed!
I do - have to enter too far in advance to know whether she will be in season, anyway. My girl jumps best when she is in season (but is horrible to do dressage)
most of the time i did with my old girl - although there would be occasions i would avoid going to shows if she was having a particularly 'marish' season...