You can minimize your loss of draw weight over time by unstringing the self bow whenever it is not in use. Even the same day, unstring it if you're not going to be using it for an hour or so.
If you haven't shot the bow for more than a few days, exercise it before drawing it to full draw. In other words, first draw it about 1/3, then 1/2, then 2/3, letting down after each short draw, before you draw it to full draw and shoot it.
The max draw length on a self bow isn't just a suggestion; it's critical. Don't ever let anyone draw it past the max recommended draw length.