I only sanitize in the spring (filter removed) - after de-winterization.
If the water started to taste or smell funny - would do it again. I would then change the filter too - otherwise it'll last all season for us.
I do empty my fresh water tank when I park it for more than 1 week, I simply remove the drain plug underneath. I then fill it to 1/3 full with fresh water before leaving on a trip - I should watch MY weight more than my trailer's...
Has worked well for us.
Denis & Diane
2010 Sabre 31REDS
Ford F-250 2011
* Happy Campers *