On my ios version I've tried everything with my 60 year olds but they never have kids anymore. It took so long between all four of their kids especially the 4th one who was pure luck at 45 by the time I wanted a 5th, they were reaching 50 and just completely stopped. Baby boosts just wasted my money. :p On the other hand with my pc version, my couple never had to use boosts but had two sets of twins and one separate girl.