DD2 is sleeping in DD1s crib with the same mattress bought in June 2007. Like your LO, DD1 was not a jumper and is such a lightweight that she didn't even make a dent in the mattress. I have no concerns with putting DD2 to bed on that mattress every night.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.