If technology is obsolete within 5 years of purchase and we scale that lifespan to the human lifespan of about 80 years (like we do for cats and dogs) then we find that there are actually 16 "tech years" per Earth year. It gets worse if you consider the usual 3 year desktop computer replacement cycle, which then works out to 26.6 tech years per Earth year. A standard mobile phone contract expects the handset to last 24 months, making 40 phone years per Earth year, or 3.3 tech years per month. If you're an upgrade-happy young-'un who upgrades every year, you might be shocked to learn your phone is aging at a rate of 6.6 phone years per Earth month, and the super-quick upgraders who can't stand being with a handset for more than six months mentally age their phones at a whopping rate of 13.2 tech years per month. This demands a graph.
Mokalus of Borg
PS - Another friend has suggested that "tech half-life" is 3 months.
PPS - That would be useful if you knew how much "tech substance" was there to begin with.