If you're smoking that much of the same strain every night you probably have built up a significant tolerance to it, so more and more is needed to get the same high. You can avoid a tolerance buildup to a large degree if you switch off strains on a regular basis. Personally, I never smoke the same strain more than two days in a row and never have tolerance issues. Every time I grow a new strain I always put some back and have built up a collection of over 30 strains in my stash. Usually once I've smoked a given strain I won't come back to it for at least 1-2 weeks, if not longer.