Rose Aphids, Second worst bug on the planet, second only to mites. Hate them.
Anyway, how long the pea plant last depends on how many adult aphids walk over to it and start breeding. I'd say a couple of weeks, I certainly wouldn't bother planting it in an enclosure, I sow about a dozen seeds every couple of weeks. Problem is if you use a brush to get the aphids off of the pea plant it does a lot of damage to the tender little pea plants and can shorten thier life. As far as quantity of aphids, It takes about one small plants worth of aphids to make a meal for an adult tinc.
I am going to try, and would suggest ordering a pound of Fava beans. They are a member of the pea family and are a much tougher plant.
Joe