We used Big Yellow for a couple of years. It wasn't cheap but it worked well for us. We had a smaller unit initially then upgraded to a bigger one. We paid extra for 24 hour access - otherwise you can only pick up /drop off stuff when the reception is open Choosing a place nearby and with easy veh...
Bear in mind that you may not get the gap you want - you will be older - it may take longer to have a successful pregnancy.
What if you aim at 3 years and get 4/5 years?