Is NAN overvalued?

I'v been a holder of NAN for 7 (or so) years and started with shares around the $0.40 mark and have averaged up along the way over the years. I'm in the fortunate position in that my holding have grown a large % and now make up a large portion of my portfolio. I am currently torn, I am deciding whether to sell 25% of my NAN holdings to lock in profits and free up capital or just sit tight.  On one hand the P/E ratio for NAN is very high and from that alone you could argue they are over valued. On the other hand their market cap doesn't seem unreasonable given their IP, regulatory approvals, the revenue generating products already in the field, the near completed R&D for two new upcoming products and a bright future.