As a frequent flyer from BOH I can tell you that you rarely see any of their aircraft standing idle at their base. 2 of their 737's are leased to BOH based Palmair. BOH also has a number of 747 flights operated on behalf of Bath Travel. Another 737 flies ski charters to Turin every sunday from BOH. Palmair have stated that they will be using 737-300's this summer leased from EAAC.
Mentioned on another thread, another 737-300 will be operating flights this summer from Newcastle.
To finsh off. Unless they are storing their aircraft elsewhere then they're all busy this winter period. Also the 737-200's are starting to be replaced with 300's for this summer season. Seeing as they've just acquired a further 2 747-200's I think they expect to keep them flying a few more years yet.