As I understand your last post, the 20ms switching applies to the 12/2A thing?
Is that motor running on DC or AC?
I think the ssr you pointed out, will not work for 12V (24-265 load voltage).
At http://www.conrad-direct.co.uk I found
this thing :sharp S202T01 in the solid state relay section.
But I must admit i don't have that much experience with ssr's, so I'm not sure if this one will do the trick.
If you have to stay with relays I would at least use a type that comes with a socket and have someone change them whenever they die.
Here in germany I would go for relays made by "Finder". That company operates worldwide and is not too expensive!
If your application really runs 24-7 with the relay switching on-off every 20 milliseconds that adds up in half a year to:
25 Switches p. sec * 3600 secs in an hour * 24 hours * 180 days = 622.080.000 switches
Oh poor relay 
Eberhard