What you’re saying is explicitly false about the a16z START program, which says its applications are always open on a rolling basis.
Also, as much help as a program like YC can be, if you ‘wait’ between sessions, rather than keep making as much progress as you can, you may not be what they’re looking for. (Longtime YC observers will also know that for good applicants, they sometimes act outside the normal deadlines/cycles.)
Are you using your creativity, & skill in arguing, to convince yourself things are harder than they are?
No one is saying do nothing between applications. Just pointing out that it takes time to apply, opportunities coming around a few times a year and for many startups lack of funding can hurt/kill them.
The time it takes to apply for these seed programs is days not months. Many (including a16z START & 500startups) don't limit applications to "a few times a year" nor "accept you only at certain times of the year".
And the 'etc' of your claim "[t]here is really only YC, 500 Startups etc" hides a ton of options, including this a16z START program, programs from other VCs, TechStars, & a world of other seed-level options from other individual, syndicate (AngelList), or regionally-motivated investors. And, plenty have always-open rolling, or diverse staggered, investment windows.
So you never have to "throw away 3-6 months" or "wait 3-6 months" if you're making demonstrable progress on a good concept.
(Sure, once you've got a big burn rate, fundraising is likely to be a year-round time-suck with many-month closing cycles. But that's not the "even if you don’t yet have a fully formed idea and haven’t yet quit your day job" point this early-seed "market" targets.)
Also, as much help as a program like YC can be, if you ‘wait’ between sessions, rather than keep making as much progress as you can, you may not be what they’re looking for. (Longtime YC observers will also know that for good applicants, they sometimes act outside the normal deadlines/cycles.)
Are you using your creativity, & skill in arguing, to convince yourself things are harder than they are?