I only know that E is not something that I personally would try, however about the high not lasting as long as it used to for you, heres what you should do:

1. Take a week or 2 break from smoking pot(this will bring your resistance WAY down)
2. smoke higher quality bud if possible

if you follow those steps, you will be able to get high of only a few hits and it will last you MUCH longer, probably around 3 hours again. GOODLUCK!