SakashiroBurstarI wouldn't use grade A collectors for mining. All the added weight and range gives you is downtime when they decide to go chasing after something very far away, which is itself just more opportunity for them to bang into things. Grade D is lighter and more than enough for what you need when mining.
A-grade collectors last two minutes longer.
With how cheap limpets are-and the fact that if you're efficient enough, you'll need to dump them to make space- it's better to roll with C-grade collectors, a nice middle ground between D and A.