Nikrod, I have not checked in fund's prospectus, but to me it seems logical that they charge this expense on periodic basis (quarterly or yearly) to long term holders. and to short term holders as a part of exit load.
Maybe the accounting appraoch for expense charging is given in their prospectus in small print.
Until recently fund houses used to charge variable expenses per day and make sure that sum was equal to expenses per year. This was beneficial to some institutional investors wherein, for the days they invested in such schemes, lower expenses were charged. This was part of the mal-practice by AMC's. SEBI has recently barred this and manf=dated fund houses to charge unit holder uniformly (every day). Logically speaking, if AMC's charge expenses on quarterly basis, some big players would churn their money in less than 3 months in order to avoid these expenses. Also some corporates make investments for periods as short as 3-4 days. That is why AMCX's charge expenses on daily basis.
SEBI also mandated one more rule regarding exit loads few months back. Earlier the money from exit loads was used for fund expenses. Now AMC's have to add that money to funds net assets and add it to NAV accordingly.
I don't know about prospectus's. Maybe they print the infi in small font someplace where people surely would not look.