As an alternative to using tablet containing CYA and experiencing a buildup which, according to the local pool store personnel, is only resolved with a drain/refill, is it harmful to use shock as the only chlorine source?

I dried it to about 1/4 full last summer and still tested high on CYA so for about the last month of the season I only used shock with no noticeable ill effects. Just wanted some additional input as I get this year underway.