thanks for your replies
the reason I asked is that I think that if I spray some cleaner on the toilet every day, I think it doesn't go so bad so quickly
.... as when I recently went away and I don't think the toilet was cleaned once in 7 days
& I had to unscrew the whole thing on my return because of the smell & was surprised to see crusty stuff
(but I cannot remember how many weeks or months before going away I had unscrewed it to clean under ....)
am probably going to have a sort of test and try to unscrew it again exactly a months after I did it last
(when I will have sprayed the toilet most days- I didn't today but we were away most of the day- )
to see how it compares visually with the last time I unscrewed it ....
why am i so concerned about that ????
is it just because I want to track the smell ?
(I don't want to try to cover it with blue water and/or other bleach stuff one can drop in the tank ...)