Have used the finnex heaters from Kens Fish and like them. That is what I had in all my tanks for almost a year with no problems, then all of a sudden I had 5 out of six burn out.(all with in the same week) The heating element part seems to burn out on them. So they seem to last about a year.
But have to say they kept the tank with in 1 or 2 degrees. If you go with them I`d keep a few spares around to have a back up.
I am thinking of trieing the deep blue stiks that Kens has next.
Larry