I have only been smoking for a couple years, but most of it has been in my last year. I definitely remember the first few times I got high throughout high school, compared to how high I get now. The first time I smoked out of my buddies 4 chamber perculator bong, I almost threw-up from one hits worth of coughing, and I immediately laid on my couch just feeling my skin for like 6 hours. A year later, I can now toke a series of monster hits in a short-period without feeling very high afterward. My level of high has been pretty consistent the more I smoked though. I don't think its possible to completely lose your high.