We have 3 rams, but that is because I am buildig my flock and want keeper ewe lambs from different sires. I also bought the third ram sort of by accident, bidding on him at a show auction to get the price up for his breeder, and he ended going under the first bid. He is a well bred registered ram, so I didn't lose anything other than the look of shock and incredulity from my DH as we loaded him in the trailer after the show! LOL
We currently have 35 sheep. Half of them are lambs and yearlings. The 2019 Fall yearlings are all bred or with lambs at side. 2020 Spring ewe lambs which will breed this summer, and 2020 Fall lambs which will breed next fall, and 5 2021 early Spring ewe lambs which will breed next spring.
Al of them have different rams as fathers, and we tag them with 3 different colors - one color for each ram sire. Makes it easier to see what each ram throws with the different ewes (for culling purposes and selection of replacement ewe lambs). Also when sorting them for breeding.
One healthy younger ram can easily cover 30 ewes. The commercial shepherd wants t feed as few mouths as possible to make a profit. Keeping an excessive number of rams in ratio to the ewes is not economical. If you have a lot of misses from one ram with ewes that usually settle, check out the ram. If you have a lot of misses from certain ewes, while other ewes bred to that ram produce, check the ewes. As rams and ewes age, their fertility can wane. I have White Dorpers that breed every 9 months. Those rams don't go sterile in the heat. Certain breeds of sheep (mostly wool breeds) have a specific rutting time of year, usually in the fall as the days get shorter and cooler. Those rams go sterile in the heat of summer, particularly the older they get.
If you have only a couple of sheep, and only breed once a year, it will not be economical to keep a ram full time Also, FYI, some rams can be dangerous. I never turn my back on any ram no matter how sweet he seems to be. One of ours has developed a nasty habit of sneaking up behind us an then butting us from behind! We have had him since he was a lamb, he has always been friendly, and he is just starting this at 3 years old.
To avoid wasting money feeding a ram all year for just a couple ewes, if you have 3 or fewer ewes try to find someone who will offer stud service to their ram. It will be cheaper to pay them for stud service that to keep a ram if you are having to buy feed. If you can't find anyone who will breed your ewes for you, buy a ram lamb and use him on your ewes. Then once they are settled sell him. You can also put him in the freezer for yourself - ram lambs are still edible under 18 month old. You don't need the expense of feeding him over the winter, spring, and summer until the next breeding season. Keep the best ram lamb - long, wide loin and thick leg - from your spring lambs and use him in the fall. He will breed fine at 6-9 months old. Use him on his mother too as a terminal sire (her lambs go in the freezer). Once you are sure that all the ewes are settled, sell him to avoid feeding him for 9 months. Repeat this process every year.
I use a breeding harness on the rams and marking crayons which I change color every 2 weeks. Once the ewes no longer show a mark on their butts after another 3 weeks, I know they are bred. I might leave the ram in for an extra 2 weeks depending on how I feel about it. Using the breeding harness and marking down the dates on which the rams mark the ewes gives me a good lambing date. I can pull the ram out of the pen, or return the ewes to the main flock now that they are bred. About 3 weeks after the last ewe remains unmarked, I choose 9ne ram and turn him in with the entire flock. That ram wears a harness and crayons too. This way I use him as a "catch up" ram to make sure that all the ewes have been bred and will lamb. Keeping ewes that don't lamb is inefficient and wastes money. They need to produce lambs to earn their keep.