Near the end of true pre spawn (meaning no fish have spawned yet), the males will flood the shallows and create beds a number of days before the females are ready to start spawning, then they try to steer/court females onto their beds and will repeat this process as many times as he can throughout the spawning cycle. During this period the male is continually "fanning" the bed to oxygenate laid eggs and keep any debris from building up on the eggs and suffocating them. So, in short, the bed might be 3 weeks old, but it'll appear "shiny" or clean as long as he's courting or guarding/fanning laid eggs.
I can't say yet based on 1st hand observations if the males will abandon the fry ball to repeat the cycle for a second or maybe even third spawning moon cycle. Or if he recycles the bed, builds a new, or calls it good after one round.
But for a timeline perspective, the male is:
day 1: building a nest
day 4: courting females
day 6-8: has a female locked onto the bed, and they're actively spawning
day 22: laid eggs finally undergo "swim up" stage and form fry balls, male begins to hyper focus on the fry ball's defense and stops fanning/guarding the bed.
day 29: male has been continually guarding the fry balls
***Females can make beds as well, but it's not commonplace.
As for advice,
If you can barely see those shiny spots, just make mental notes of it and stay a good bit back and then make your presentations.
It's mind blowing, and equally frustrating how much harder the females are to catch once they discover you the first time. Way easier imho to catch big females in the "blind" casting to high percentage bedding areas.
Throw a Pegged/T-Rigged creature bait, and/or skip that whacky worm especially on the back side of docks, and under overhanging trees/bushes.
I learned the hard way at least for my fish that during the spawn (when females are actually present near a bed), moving baits aren't the best way to go. Lots of people preach to move lots during the spring and some days that's true especially after that first true wave of bigger fish spawning, but if you're fishing for bigger spawning females.....a very targeted approach with a much slower presentation is deadly, and I haven't had the same level of success with a moving bait.
Lastly, I'm no expert by any stretch of the imagination, I've just nerd'd out on the spawn as it's really fascinating to me. Most of the above is based on first hand observations on my home lake that has several feet of viz and easily observable beds. So like most advice in fishing, it's mainly applicable to my own lake and fish population 🙃