Bruce,
I have several of those DC-DC relays ranging from 25 to 100 amps.
I have been reluctant to use them in any critical service because they only cost $12

What do you think about grossly over sizing them?
For example, if there is a solar panel supply which max's out at 25 amps, then use the 100 amp SSR for switching the element load off when target temperature is achieved.
Do you think this would give the inexpensive SSR a fighting chance at staying alive more than a few months.
(I would also recommend to everyone to use the appropriate heat sink)