One strategy is to check product lifespans before buying—you can usually get at least 7ish years of updates for a Mac if you don't accidentally buy a product that's just about to receive an update. I think macrumors has a chart for this with simple "buy / caution / do not buy" indicators and history of time between updates for various kinds of products. Buying early in a model's lifecycle can make a big difference.

Another is to just buy used every couple years. Buy a 1- or 2-year-old Macbook or iPad or whatever, sell a couple years later, repeat. Average annual spending can be surprisingly low this way, after an initial higher expenditure to buy your "ticket" to this train, of course, while still keeping you on recent devices just about all the time.

Some businesses simply lease their Macs, so don't really have that problem. They'll lease a new set of devices long before any go out of support.

Overall, any budget-conscious Apple strategy has to factor in the used market. Even if you're always buying new, if you time sales right you can recover a lot of your purchase price by selling your old devices. This can seem a little weird if you're used to the used market for consumer PCs—in that world, holding on to every device until it is totally worthless makes a lot more sense, because they lose used-market value much faster than Macs.