Alimta was approved by the FDA and EMEA as a front-line nonsquamous NSCLC maintenance therapy 2 years ago (#MSG-39303562) and the continuation maintenance setting makes even more sense. Tareceva was approved in the front-line NSCLC maintenance setting a year ago (#MSG-49106892), but as you noted we should not expect that this will increase sales. Rituxan is a case in point where sales in NHL has increased a lot by use in the maintenance setting. Revlimid might have good* maintenance opportunity in the post autologous stem cell transplantation setting where therapy could last few years and is also being tested in phase III as a maintenance therapy for post R-CHOP in DLBCL.
*Tox, specificaly neutropenia and the risk for new malignancies could of course stop or lessen long term use with the drug.