A few years ago, I made a bow for a friend to the exact specs he wanted 52#@27", he called me a month or so later and told me his bow had gotten stronger and felt like it was least 60# at his draw length now. I thought "no way", he brought it over to my house and I checked the poundage, it was 60# at 27 now. The bow was made from a 20year old well-seasoned osage stave.
In all the bows I have made his bow is the only one that gained poundage until today, this time it was my personal bow that I have been shooting since 2015. With some health issues I couldn't shoot it and made a bow in the low 40s that I could shoot easily.
I started integrating "Old Faithful" back into my shooting routine today and it felt like the poundage had gone up to me. When I made it was 52#@25", I have put tens of thousands of arrows through it since, for the last 3 years it has been hanging on the wall in my shop un-shot.
After I finished my shooting session off my deck at 3D deer targets, I took it out to my shop to measure the poundage, the bow was 55#@25" now, it has definitely gone up.
I have been coming back physically and doing weight lifting at the gym just to build my bow shooting muscles. To shoot this bow I have a way to go, dropping the poundage of this bow is not something I want do, it is the best bow I ever made.