If you strain your mcl, are you more likely to have a tear down the road?

Not likely. When ligaments completely heal, the rate of reinjury is the same as the native ligament. It is important to allow the mcl to heal as a return to activities too early will lead to reinjury.
No. Once a mcl (medial collateral ligament) is healed, you should be fully recovered and particiapting in all the activities you were doing without restricitons or limitations. For a grade 1 (sprain), this may take 2 to 4 weeks, for a grade 2 (partial) tear this may take 4 to 6 weeks, and for a grade 3 (complete) tear this may take 6 to 8 weeks. Pain or instability after 3 months should be evaluated.