To your question, I locked 10k for 3 years two weeks ago. Because of the difficulties with the phase 3 rampup I missed out for two days. Since then my Raspberry Pi is working like a Swiss watch and I witnessed 3 blocks already. The estimated waiting period to find the next block is at 11.66 days right now for me. This would make it a 6% interest per year forecast.
Of course there might be also quite some 1 month lockers who don't want to keep their funds locked after that time. Time will tell where this will find it's balance but with 6% interest I'm really happy since those are my "high risk, high reward retirement funds".
I have earned 3 witness amounts with my +-25000 witness account but only locked for 6 months, I wish I had put it in for 3 years but I am going to build up to 100 000 coins and split this into two accounts. 1 for 1 year and 1 for 3 years and have 20 000 liquid. Well that's the dream for me.