i always use tulsion mb115 and changed resin early january(im DI only)and its only just started to creep up now!normally resin lasts me 4 months max.ive been using the same amount of water as usual(apart from jan due to working from my car with barrels so used a bit less).i buy my resin from gardiners these days.
i used to use pure freedom for resin but had a few bad bags(the resin started to creep up after 2 months).tap tds is between 029-035 most of the time.