Replacing radiators and draining off

[gardener1214388]

I am replacing radiators.
I note that some Radiator valves on the market have drain off points.
Is it a good idea to use these.

Drain off valves; most seem to have a rubber washer inside on a floating head and after time the rubber washer sticks, blocking drain off. Is there an alternative product that does not use rubber to seal.

 

[Armo74]

It's a good idea to put them on all the rads downstairs if the pipe drops are from upstairs.