I bike commute 4 days a week. My main bike runs 700x35 road tires. My other two bikes run 26x1.85 and 700x32. I usually top off my tires every other day I ride and find that it has gone from 90psi to 70psi in a couple of days. The other two bikes sit for a couple of weeks at a time and sometimes even a month. In the summer the 700x32 will go from 80 to 50 after a couple of weeks, the 26x1.85 will go from 70psi to 55psi after a couple of weeks.

In the summer I notice the tires loose air more quickly, in the winter they hold their pressure a little longer.

So stop replacing tubes...it's normal for tires to loose pressure over a month. And pumping to a higher pressure will do nothing to change that.