I'm crazy about rompers! I agree that there is no age-limit as long as you find one that fits your look and proportion. The key is to try on as many as possible until you find the right one. Rompers are in general for more casual occasion, while jumpers can be dressier. I have tried on jumpers that look like they can be worn to work with blazer or even to a party with jewelry and heels. However, I found a black romper with flower prints at the Miss Selfridge's sale last weekend that smacked of French charm. I felt totally sexy wearing it with a crossbody satchel bag and low heels (not to mention lace French underwear). My BF thot I looked really good in it.
But I also realised that I look less good with my other rompers when I lost weight, esp around the leg and bum area. So they may not be all for skinny girls. The key, again, is proportion.
I would draw the line at terry cloth rompers, esp the bandeau ones. They seem only suitable for the beach, or for teenagers. But other than that, go ahead and experiment!