Depends on funded or not.
I have about 40 total, but use different accounts for different sports. I can jump in and out of any of these. I have slightly less than 10 funded now.
If it was baseball time I'd have Grande and 5 Dimes funded for sure. I've been meaning to re-up at 5D. Grande is not needed for baskets and foots
If hockey time I'd have some different outs going.
I used to keep up to 15-20 funded at once, but only used a core of 5-8 books primarily. Checking all the lines takes a lot of time, and no free lines service has all the right books. Less than 10 is OK, if you have a good mix.
I'm more selective now.
I use mostly Pinn, WW, SIA,Cris, and OLY now. I need to re-up with Holly, 5D, and SKY, and then I'll have enough for this time of year.
A lot are basically the same. Little difference in lines ( not quality) amoungst shops like WWTS, Grande, Royal, Jamaica, Gameday, and dozens of others. I'm a bit iffy on Canbet, and the new guys.