I can't imagine why any guitar would take much time to "settle in" when retuned, even significantly. I would suggest being sure you wind plenty of string onto the pegs when you change them next ... I find this can help with reducing 'slippage' ... I'd also suggest when you are retuning that you try a firm, but gentle pull up on the string, one at a time, and refine its tune ... I find this helps strings 'settle in' better ... if you still have trouble I'd have a luthier look into it. You shouldn't be having too much problem, there might be soething amiss.

The electronic tuner idea is a good one. As good as anyone's ear is, the electronic tool is not affected by our tendency to 'sweeten' a tuning and make slightly imprecise settings which are only compounded when we tune the next string/s.