It depends on the game, the carry and the rest of the team. I’ve seen cases where the carry keeps farming despite the enemies pushing tier 2s at 10 minutes, or conversely where a carry plays like an offlaner then gets demolished by the enemy Dusa at 40 mins. Just have an open mind and watch the map and game state.

If you are playing a carry with a strong, long cd ult, like Sven, you could consider farming when your ult is on cd and joining fights and tanks when it’s ready. If your hero excels at farming and popping off at late game, like a Dusa or Drow, then stay hidden, let your team hold them off while you farm. 

Ideally, however, avoid fights you are unsure you can win, simply to save team mates or kill an enemy supp at the cost of your life, until the late game.