And I had one boarder who chose to pay an entire year's board in advance
When I was boarding, the owner of the property wouldn't let us do that! They'd just rid themselves of a really bad boarder who never came out [it was all DIY self-care in a pasture so coming out to see the horse was part and parcel!] and I think they were terrified they'd get themselves stuck in the same situation if we paid ahead.
Once we got into the rhythm of paying monthly, once the property owners had had a chance to see we were good boarders who, y'know, actually turned up every day to look after our horses, they would have let us do it, but we didn't ask again. Such lovely people, it was almost a shame when we got the lease on our current ten acres because it meant we didn't get to see them daily any more!
Mum liked to pay long-term because it secured the boarding. She'd been kicked out without notice a few times [for no reason!] and people are less likely to just up and kick you out if you've already paid. But I find that if you board at an actual barn/center instead of random private properties, you sign a contract, and it's easier to get the property owner to stick by their side of it!
From the other side [I work at a center] it's much easier to have a contract to ensure you get paid and to make sure that your boarders understand exactly what they're getting for their money! My boss charges a lot, but all hay, feed and rugging is included, and fly masks on/off as necessary, and individual pastures. Some boarders pay a little extra to get special suppliments, like one horse gets brewers yeast for his extremely sensitive stomach and another gets MSM to keep his joints working properly, and other boarders pay a little less because they supply their own basic vitamin/mineral suppliment. There's an extra fee to use the arena, which every boarder understands as this is laid out in the contract and marked on the "arena booking" whiteboard/notebook. I don't know if she even charges a late fee - she's nearly always full, so it'd be easy enough to just kick a boarder out if they weren't paying their way.