They can... 10 months is a good period of time. I dried my little Nigerian up so she could have a month off before I put her in with my buck to (hopefully) be bred. So she was only in milk for 6 or 7 months this year.
I was always interested in having heritage breeds on my mini-farm. I would love to have a heritage dual-purpose cow. Dexters fit that bill...but so do Red Polls. Neither of them are exceptionally common..or cheap. But options abound, so who knows.
Love talking breeds! We have GOS cross pigs. We are going to breed them to a Berkshire boar. We have Dominique chickens and are hoping to get Dorkings for the spring. Also Black Spanish turkeys. We are going to get a Bourbon Red tom for the hens, also probably in the spring.