If it's regularly deflating, even a bit, then it'd be well worth it IMO. I was amazed at the difference having really solid tyres made. (makes sense really, of course - the harder & therefore rounder they are, the less tyre surface is in contact with the road, & therefore the less friction is there to battle against. But I hadn't really thought about it that hard :-) ). I intend to start pumping them up regularly on Sundays, rather than waiting till I notice flatness.