Deferred spending is often a good idea! Especially true if one has to ever put any of that spending on credit.
So I would say it would be a great idea in many cases but you do have to make some personal decisions on how it may fit for you. Changing out a few of the minor parts can be a real money saver if done carefully. first step might be to decide which parts are a problem to you. Many of the cheaper commercial sets do have some real questions for the minor items like needle valves or solenoids and it can make a great improvement to change one if it is giving you trouble. Spending $20-50 now versus spending $220 on a credit card is pretty much a no-brainer but you can get more value even there with some careful shopping and decisions. I like the idea of looking, researching and buying at the right time when you have the option. With luck you might find a great needle valve, for instance, at half the cost if you do some careful shopping and get a bit of luck.
The downside is that you may also have to spend a bit more time and effort when changing out a bit here and a bit there. Upside is that it does come much easier as you go along and learn details of what works best.
I highly recommend what you propose. And while looking for one item, keep the eyes open for great deals on some of the other parts by looking at the reg setup as a group of parts, rather than a single item as they are often sold.