I used to bump in to one of the girls that worked at Robinwood from time to time, she seemed to really enjoy it and managed to get out quite a bit.
There is loads to do at the Bridestones and from Todmorden you can walk there fairly easily.
You'll be able to get quite a bit done as invariably you can always get something done apart from on wet days but the same goes for anywhere I guess.
As for 3 months, you'll probably get a bit sick and tired of it by then but you can always go over towards Widdop, Clattering Stones, Dovestones, Gorple possibly Scout Crag depending on how it stands with CROW now.