perhaps you could just lift the front (leave the sides and back attached since it is holding well) and clean the very front, reapply new glue and be good for another few days. Many people re-do the front only every 4 days, that is not uncommon.
The front gets that greyish color because dirt is sticking into the glue and building up...you could try using a thinner coat of glue but you may be right....4 days may just be the time that it takes for YOUR body chemistry to break down the hold.
I wish I had some magic words to help you out and make your front attachment last longer, but sometimes it is just a matter of works for YOU.
DebbieS.