When should councillors be deselected?

The Yorkshire Post report that a long standing Conservative councillor in Calderdale, Grenville Horsfall, has been deselected from standing at the 2010. Cllr Horsfall is 73 but ageism doesn't appear to be proven (at least not to his detractors, Cllr Horsfall himself seems to have engaged in a spot of ageism denouncing his deselectors as "wet behind the ears"). The grounds are that he has gone too far in publicly attacking the Conservative-run Council. Also that he has not done enough campaigning (he denies the latter charge claiming to have recently delivered 3,000 leaflets with his fellow ward councillor.)

Rather difficult to judge the merits of this case on the information available. But generally shouldn't more councillors be deselected? Usually those who seriously fall out with their Conservative Groups are dropped. That is inevitable if a cohesive team is to operate. But what about those who might not cause trouble but also simply don't pull their weight? Aren't there too many who just turn up (or often don't turn up apart from for the absolute minimum attendance required) and take their annual allowance?