Even more than sheets, the life of a towel is hugely dependent on circumstances. 70 to 120 washes is about right though they can last longer, but you can also ruin them in 50 washes.
First only use 100% cotton towels. Might sound obvious but there are towels with polyester in. The trouble is that polyester is oleophilic (attracts and absorbs oil) and will quickly go grey if any stray oil gets in the wash. If a stray oily rag got in there the result will be ruin and you will not be able to wash it out and whiten it.
If you are going to do your own you will ideally need 4 complete sets. If you use 30 bath towels to make up all the beds you need 120 in total: 1 set in the room, 1 in wash, 1 on shelf, and 1 for emergencies because you won't be able to ring up for more.
So you have bought enough good commercial grade towels. What now?
When new, wash at a high temperature, (80-100c), with plenty of detergent, followed by a cold rinse (opposite of my advice about sheets). This shrinks it and locks the fabric loops together. You can cut off any pulled threads.
Tumble drying is preferred; this will help in "fluffing" the pile, but don't over-dry as that will result in a harsh, dry feel, and excessive wear on the hems.
Never, ever, let dishcloths, teatowels - any cleaning items in with wash - fats and chemicals kill towels.
Towels need plenty of rinsing to remove all suspended soils, soaps, detergents and alkali.
Do not store wet towels on concrete floors, or on timber (or other porous surfaces) as this will cause staining. Again sounds obvious but...
Like sheets, whiten only when you must and only whiten those towels that need it - don't add extra whitener to the whole wash unnecessarily. Detergents designed for white only are good as they can use more optical brighteners. Ultimately there are so many things (like the waters alkalinity) that you cannot control but can make a huge difference to whiteness and detergent's ability to work.
Only leave towels in the sun until not quite dry and then finish with a tumble. Our strong sun can hurt the cotton, especially in the hems. It can also bleach towels white.
It's not easy doing your own laundry, many give in and return to the easy care and consistent quality of a good laundry. But if you have good equipment, good quality commercial grade linen, time, patience and maybe staff to help, it can work if you're careful.