I spot clean at times also, unless they've managed to slide thru it & track it all over, lol. Some of my snakes deliberately defecate in their water bowl, & some leave "their gifts" inside their old skins when they shed- even better!- if only they'd do that more often.
Spot cleaning only goes so far, if the substrate has been widely contaminated. But sometimes you just cannot drop what you're doing & clean the whole enclosure- in that case, spot cleaning for the time being is best, & do the full treatment as soon as possible. Just remember that our snakes are trapped within- to keep them healthy, keep them as clean as possible.