If you have lush pastures where a cow can eat on less than 2 acres all summer twins can be a blessing but if the cow has to work hard she will not be able to raise twins and breed back.
I love twins here as with my small pastures I try to rotate when the grass gets down to about 6" to 8" and water is never over 100 yards away.
I have 18 cows and 1 bull rotating thru about 50 acres of pasture which is cross fenced into about 6 to 8 acres per lot and I have a 16 acre hay field that I leave the last cutting on and I turn the cows on it to calve in the spring as it is very easy to watch.
Last year I loaned 2, 6 acre pastures to a neighbor as my cows could not keep up with the growth. He used them in the spring and they rested the rest of the year. This allowed his pastures to get a strong start. They have about 3' of grass that has fallen over and will be used this spring.
Several of the farmers in the area put many more cows per acre on their ground then have to buy hay or cut a lot of silage and complain they can't make money on cows.
I admit I baby my cows but they always seem to make a profit for me.