The second figure(the age at which one began to spend seriously on the hobby), I was hoping to distinguish from the age at which one first acquired a memorable system. The inflection point for spending is more helpful in measuring the arc of consumer spending that’s necessary to sustain the industry.
For example, at 15 I built a nice pair of inexpensive Altec VOTT speakers that I would consider high-end even by today’s standards. After holding those for ten years, a pair of ESS AMT1s. Then ten years later (at age 35) after picking up my first issue of TAS, I renewed my visits to the audio shops with reawakened interest(and more disposable income) and launched onto a ramp of unabated expenditures that substantially define my lifetime contribution to audio industry GDP. For those of my boomer generation, I sense that the bell curve of serious spending is typically age 35-65.
If the industry is to survive, it needs to find similar arcs of consumption that begin in the peak income years and extend at least to retirement.
Posters so far suggest several age demographics. Notably missing are those above 65-- who likely represent a significant share of posters on this site, but may be reluctant to declare their age.