every 6 to 8 weeks.
When making a program, there are 3 cycles to utilize - micro, meso, macro. Micro is like 1-2 weeks at a time. Meso is like 6-10 weeks at a time, and macro is 6-12 months at a time. You can plan a small deload or rest week after each meso (or can make them 12 weeks long, with a deload in the middle and again as week 13 before the next meso). During the training phase, you can periodize your training so you're not going to near failure always. Some weeks you can go higher reps at 80% max, and others you go 90% max lower reps and grow. Several different ways to periodize too: linear, undular, etc.
Takes time to learn, but at our age once you start feeling slightly down, take a week at a lower weight to back off a bit, then go back hard. My wife is the same age, and we've learned that every 4 weeks is good for her to take a deload week to prevent overtraining which comes with total body soreness, poor sleep, etc.
(to be clear, it's quite nice to see you're listening and engaging now. No matter how much shit I (or others) give you, there's an element of desire to see someone do awesome, and seems like we all want that for you too)