Yeah, that's known as tachyphylaxis, acute tolerance and happens with many psychoactive substances.
I don't know if it's possible to give an exact amount or even estimate of days meth will stay active, this is very different between individuals. As you might know, people with ADHD get stims prescribed and some have to fight with the same problematics recreative users face while for others the drugs stay effective for months or years.
When I was prescribed methylphenidate or d-amphetamine for (legitimate) AD(H)D, and if I used them alone, then after a week at max the efficacy was down to 1/2 or so, and after maybe 3 weeks the effects as well as side effects were almost diminished. Now if I took a NMDA receptor antagonist (dissociative) like DXM or memantine together with the stimulant, its efficacy was preserved for much longer. With DXM (100-200mg/d) and methylphenidate (18mg) I had to stop after roughly 3 months because of overstimulation and chest pains but no diminished efficacy of the MPH at all. Memantine is much lighter on the body and mind, medically prescribe able and can be ordered from online pharmacies. DXM is available OTC and might be interesting if you're somebody who doesn't mind a nice trip. The combination was quite empathogenic and warm due to DXM's serotonergic effects.
As a side note, DXM + meth aren't safe to take together because both are serotonergic and might thus induce serotonin syndrome if you do too much, too fast or are susceptible to it. I think that it's exceedingly rare when you limit yourself to the lowest dose possible/necessary of both agents and specially if you have pre-existing tolerance but it is relevant to taper up instead of just guessing a dose and taking it.
I myself got warning symptoms of beginning serotonin syndrome when I did DXM on top of fluoxetine but never with stims or venlafaxine. I'd say SSRIs are more dangerous than meth. It might be worse for the body to take ever increasing doses of meth than some DXM.