My 9-month old is barely under 17-lb but already 29-inch at her check up. Our Baby Trend Flex-Loc infant car seat only holds up to 30-inch. Any experiences in fast-growing babies for car seats? We didn't anticipate getting the next stage so quickly and thought the infant one would be useful up to two years. I've been researching so do we need to look for the convertible car seat and / or booster now? I know rear-facing as long as possible is safest. Any suggestions on products, longer-term but still reasonably priced. The "All / 3 in One" are double or three times the price.