I have a bib hierarchy: some older/cheaper options that I only use indoors for <1 hour workouts, some pretty good ones I don’t mind on longer rides, and my very faves (Assos Equipe RSRs) that I use for longer rides and races. About 8 total pairs in the rotation currently.
My general rule is, if I find myself doing laundry just to wash a specific item, I should get more of that item.
8 pairs of bibs from Castelli - all with the Kiss Air 2 pad, 3 pairs of NoPinz aero bibs for summer riding, 4 pairs of DHB bib tights for cold weather - anything below 15C and the knees stay covered and 5 NoPInz TT skinsuits - although only 2 get used in open races. The vile bright yellow one is for evening club TT where sticking out in the fading light is vital!
One.
Usually, if anything more than an endurance ride or if it’s hot, I rinse my bibs and drip dry in the shower before I put them in the laundry basket - lessens the smell and grodiness.
2 of each kind, so that hopefully they mate and create more without me having to buy more…
2 that I love the most
2 I use indoors
2 with pockets
2 pairs of tights
I wash each pair immediately after use, so if one is not dry yet, its “friend” is available.
3 Pearl Izumi
3 Kitsbow
16 rides per week, but 10 are a 4 mile one-way commute that I don’t really wear cycling kit for.
With my typical riding schedule, I only need 3 bibs (I never re-use bibs). But I have 7. I’m into cycling fashion as much as riding, so I have to match and I don’t like to mix brands (unless one of the pieces has minimal to zero branding). They’re all summer bibs as I’m a fair weather rider (but it’s fair weather almost year round here)
I have 3 pairs of older bibs that I use for shorter rides, 2 pairs or newer bibs that I use for longer rides, and 2 pairs of cargo bibs that I use for gravel or a morning when I know I’m going to take a lot of pictures. I also have 2 pairs of bibs I don’t much like that I can use in emergencies. I do 5-6 rides a week.
One thing that I think a lot of people get wrong is they purposely wear their old bibs indoors, which is where I think having the newest pairs is best to reduce pain. Saving the good stuff for outdoors is backwards, imo, because outdoors you shift and get out of the saddle more.
I tend to buy and retire 1-2 pairs a year.
Except underpants. Running out of those is my hint to do laundry. If I have too many pairs, I wait too longer to do laundry, and end top having to do 3+ loads at once.
I now buy 2-3 pair a year when they go on sale. I ride typically 4-5 times a week year round.
I have 6 really good bibs.
I have 3-4 good bibs starting to show there age.
I have 4-5 older bibs, not worn out that are just not as comfortable but I haven’t thrown them out.
I find I prefer the Le col bibs as they just last better.
Assos were nice but they don’t last as long.
The castelli bibs just seemed to wear out more indoors.
None of these were cheap bibs but always bought on sale.
I don’t own tights which is likely odd as I live in Canada. If I am riding outside it is 10 Celsius or more. I dont have the desire to ride outside when the trainer is all set ready to go.
Had to read that twice, as initially I thought you had 8-10 kilts for riding in.
And wondered if the same rule goes about not wearing anything underneath…
I rode one main pair of bibs this summer, reverting back to an older pair if I happened to ride before they were washed and dried (usually managed this over night)
I was surprised to find the lycra starting to go see-through at the back by the end of the summer, giving everyone a nice view of my ass.
I’ll probably chose something different when the weather warms up and get two pairs with the hope they at least last the year this time 
I have at least 10 and only three of them were actually affordable (the black bibs), most were affordable because of a sale on a weird color or previous versions.
If I had to pare it down to just the ones I use most then it would be:
That covers a mid-volume training plan doing a wash once a week. At a push could also trim down to just 3 pairs and wash on both off days.
In reality I’ve got that plus a load of other bibs that have specific use-cases (cargo, 3/4, tights, etc.) I rarely make it outside more than two days in a row during non-summer conditions, so as long as I have 2 pairs of each to suit any kind of weather then I’m pretty well covered for year-round riding.