First, I start every workout by doing 1 or 2 main lifts which I am trying to improve and base my progress on. This question does not apply to that, but everything after which would be considered the accessory lifts. I've pretty much always done #1 below, but are there any pros/cons to #2?
1) Keep the same lift for 3-8 weeks and try to improve on it each week 2) Pick a different lift each week for the same movement and just ramp up to failure, if you feel like doing the same several weeks in a row that's fine too but free to change if you feel like doing so that day.
Could you give an example of a typical week's worth of lifting? Like what days you do what and what sets/reps and which accessories you choose?
I sort of understand your question and I usually pick the same lift week after week. I've tried changing the movement like from incline bench to flat DB press (both working chest) but I find now doing the same lift I'm more wired in to progressing and I focus on progressing in that lift and that I'd only consider changing the lift if I hit a plateau.
Well here is one example of 1 day of a new program I just started, basically 3 sets of 10 I will change the reps eventually once I work out the setup better.
Pullups DB Rows Lat Pulldown machine* Incline DB Curls* Reverse BB Curl Seated Calf raise*
If I was changing the lifts i'd probably keep about half the same for a month or more then the ones marked with * change every week to a similar movement of whatever I felt like doing that day and what equipment is not in use.
I believe if you're just changing the type of accessory work exercise then that is okay. I'm not sure what your final goal is but I imagine it's something like "get stronger on basic lifts and either gain muscle/lose fat in the process". That's fine.
Main thing is your major lifts need to keep progressing and it's perfectly okay to change around the accessory work. But try to do more free standing, free space work rather than single plane, isolated, cable work. Not always, just something to think about. Again I don't know your lifting experience.
When you're stalling on the main lift it could be time to look at changing exercise, making sure you're eating enough, sleeping enough, then deload etc, in that order. Sometimes we stall on lifts, but I find it's just an off day usually I'm okay at the next outing.