My maid is 57 years old. She has been working at my place <1 yr, and I am still planning to renew her contract later (she will be 58 years old at that time).
I have a 1 year old boy and he is very energetic. Both my husband and I feel exhausted every Sunday when she is on holiday. But she has enough energy to take care of him everyday.
So I think it really depends on how helpful your maid is. If she doesn't want to renew her contract, I will consider to hire a 40+ maid. more experienced and no need to teach.