There is no cure all for sealing an aging driveway. I inherited a fatally neglected driveway when we purchased our house. Well past its prime, this modest slab has become an ongoing project of trying to avoid replacing the whole thing. Some years later, my cumulative efforts have started to yield a stronger, easier to care for driveway.
The journey has led me through a whole lot of products that are a complete waste of time and money. The best tip I ever got was to use asphalt sealer as crack filler. It costs a fraction of what is doled out in those little liter bottles and is of much higher quality. My freshman attempt at sealing used a whole lot of those bottles and it did not even last two years. I can report that after eight years and four sealcoats, the sealcoat / crack filler method works well.
Hot liquid fillers are superior, given the time and resources, but if you are buying multiple pails of sealcoat, you already have the product on hand and will most likely have leftovers. To reinforce this method, I use a layer of trowel mix across the top of all my seams. This is by far my favorite consumer asphalt product, if applied correctly, it as strong as your asphalt. I have rebuilt aprons, depressions, divots, and failing edges. When we removed the turnaround from our drive, large sections of this product remained intact even after being hit with a sledge.
The additional trowel mix step is important because unattended cracks sink from water washing out the sub base. The trowel mix levels out the surface and allows the water to shed the way it was intended. In more complex scenarios, I use several drywall knife sizes similar to applying joint compound.
It may sound like I have mastered DIY asphalt repair, but there is an Achilles heal. All commercially available sealcoats have a terminal thickness. So be warned, if you get addicted to that deep black magic, it comes at a high cost. The topcoat will lose its elasticity and the entire surface will flake off. The ten year warranties are bunk as well, even with the best conditions, it will need maintenance every few years.