There's nothing wrong with 2018 fleeces if you have stored them properly! Have you checked them over for quality? Some Heb fleece is wonderful and some, as Sally says, is already felted on the sheep (this can happen if you don't get them shorn early enough).
Yes, potholes can be filled with fleece and Heb is the perfect candidate. It can also be used for repairing muddy paths. You can line hanging baskets with it, or I use it to keep the compost heaps warm - although I have never had it rot down properly. If you use it as a mulch make sure you remove it before you rotavate!
I have to admit that I have so many Heb fleeces that I use the stinky tup ones and any badly felted ones as an addition to the bonfire - I know, naughty me!
I always check over my fleeces carefully straight after shearing, and with only 6 sheep you should be able to give them a quick once-over. If they have nice long locks, the same length roughly, and not too much vegetation in there, then leave them to dry in the sun for an hour, then roll them, push them into a woven polypropylene feed sack or similar (no holes), label, tie up the top tightly then hang them in an airy, dry place such as a barn (not dumped on the floor). They will keep for several years like that, so you can build up your numbers gradually each year and by the time you've finished at Uni you should have enough to send off for mill spinning. This will give you a quality product to sell, Hebridean knitting yarn, which is a rich dark brown and makes wonderful outdoor jumpers. The finished balls of yarn look so much better than raw Heb fleece, especially if it has black alpaca added to about 15%