No - the season end at the end of March - although if, and it is a big if, the snow is still around then the lifts will remain open, however none of the tour companies run in April as the chance of snow is not great.
Althoug the tour operators season finshes end of March we booked flights and hotel seperately and the lifts in Bansko stayed open till about 14 April. There was still snow up there just became a little bit slushy late afternoon time and the ski road was shut but other than that it was great.
Must have just missed you Dawny... we skied there until 16 April last year...
If you're an early riser then get up and ski the morning and through lunch. Take food at around 2.00pm and then have a lazy afternoon in the piste bars toppping up your glass and your tan! However, if there is no sun then the afternoon skiing should be just fine.