after re grouting my bathroom wall tiles i was browsing around my local hard ware store and came across tile grout sealer and was reading the label and it was stating it would keep stains mildew etc from the grout for 5 years. is this stuff any good or is it just another gimmick as its expensive . if it is guenine and does what it says i will give it a try ,any one tried it and would any of the professionals on here recommend it