I have spent many moons trying to get to FL at budget levels.
I like the poster who said to come up with a budget, then tweak your plans. There's no 'right' answer, and that may be part of why threads like this get contentious.
For me, I'm happy to go three days, but no offsite condos/living on granola bars. (i.e. eating on the SUPER cheap) To me, it's no vacation if I can't have a good meal.
You have to figure out what compromises work for you. Often, reducing costs results in something unpleasant- like buses, or a timeshare pitch. Ick! No thanks!
We' ve stayed offsite - in a hotwire deal hotel that included free breakfast (or ate muffins in the room). I've also stayed club level at the GF. One year, we specifically booked nine nights at Pop w/free dining (+10 day hoppers). THEN I found a 6day offer: club level at BC (5 day non hoppers) at the SAME price! Guess which one we picked?
Soemtimes flying is the least expensive option when you consider time costs. A short answer to your questions is that when it comes to WDW, time=money, and often saving money = time. If you only have a few days off work, driving might not work. (Also price out the option of renting a car near home. Sometimes that's less $ of all.)
A HUGE avenue for you to consider is making sacrifices back home to pinch pennies. Each time you sacfrifice- credit yourself $. Each time you skip movies/eating out, buying clothes (or use thrift shop), trim utility bills, skip splurges like hair/nails, clip coupons, skip getting the newest phone/new things for your phone; all those choices add up to a better vacation. (though less is not always more, sometimes cheap junk is just junk)
You can also spend more time shopping for deals. I'm not a fan of eating junk food to save money, but sometimes you can save big by making an extra effort. Like I regularly shop at two different grocery stores, AND a roadside farm. Again, my Time = Money. One store has grapes at $.99, while the other has them at $4 a pound. The famer only has (certain) produce, but the quality and prices are excellent. Eggs/vegetarian meals are far less $ than steak, and are healthy to boot!
My thinking as to once I'm on vacation actually now tends towards making the MOST of the time I have. I'd rather stay three days onsite than cooking all my meals in an offsite condo, with no daily maid service, driving back and forth to WDW, compromising lots of time in the process.
Last, I dont think the person who said you shoudl consider putting off your vacatio is mean spirited. LOTS of folks on the DIS use that very strategy as ameans of getting the most out of it. The longer you 'plan,' the more value you get from anticipating your vacation, and the more time you have to save. Once the vacation is over, it's over. I would not be in a rush to do it too soon. Dreaming of a vacation is free! It's the doing that gets pricey. The DIS is full of dreamers, plenty of folks plan two years out.