esshup - it greatly depends on the quality of the diluent (water) that you used in the spray-tank.
"Clean water" (no suspended colloids or excessive microbial organisms) will usually allow the "in-tank" glyphosate mixture to retain its nominal level of activity for several days, and possibly weeks. Otherwise, glyphosate will either bond with clay particles and/or suffer microbial degradation at varying rates & levels.
