Dd1 is 3 in august and we still lift her up from time to time. She can climb into her car seat however if I'm in a hurry and can't wait the 10 minutes it takes for her to stop mucking around and just climb into her seat - I pick her up and put her in it.

She mainly wants DH to pick her up anyway, he is her favourite, but I usually have my hands full with the other little ones.

If it helps though - my SPD was nearly nonexistent in my 4th pregnancy, compared to how it was in my 2nd and 3rd so it might be better next time round? I did have weekly chiro treatments after dd2 and during the pregnancy though.