Straight forward question

Should Check valves be used in central heating rad feed pipes?

The engineer added them (a ) to ease removal without draining (b) while waiting rad delivery so we could use the heating at the time.

Fitted 9yrs ago one leaked after 4yrs and now started leaking again, this one is in the return pipe.

Now I've said that, bet the other bugger leaks now.
Many thanks. I should say I'm in UK, not that it makes any difference.

Bob, March 2014