about tsst&tran analyze on vco

Today I found some questions when I simulated one LC VCO using Mentor EldoRF:
1、I found the vco need 2.9u when it oscillate,but it get to most amplitude only pasting 2n in tsst
2、how long will the vco oscillate ?Mine is 2.9u,but i found most are some "ns"
thanks for your answers!