I have had a 5.6gpm hot water skid for over 7.5 years now and have had great luck with it.
I bought it new.
I just had the packings and some brass changed out earlier this year so I got a little over 7 years out of the original packings.
I had to have the transformer changed out last year, changed out an unloader last year and had the coil de-scaled (actually rust was clogging the coil) and that is about all I have done to it.