I would just keep in mind the fact that the lessons you do today are going to all come back roughly six months from now, so make sure that you’re factoring that into your speedy start. Even if the reviews are easy, higher review counts can add more pressure. But if you’re fine with that and aren’t worried about that for the items you feel you know very well, I think rushing at the start is fine; just make sure you ease up a little once you’re out of the very easy stuff, or you might cause problems for yourself down the line.
As far as transitioning to a more steady pace goes, I’m seconding wct’s advice about choosing a pace you can maintain through your entire WK journey. I’m a pretty strong believer in the “do a set number of lessons every single day” strategy. I went from 13 to 12 to 11 and now 10 daily lessons, as the number of items I have in circulation has gradually increased, and the number of vocab items per level has decreased.
What this translates to is that I level up about every two weeks, which is perfectly fine for me. I’m set to reach level 60 around March or April next year. I’m also set to be graduating out of the beginner stage a month or two before then, and will be starting my intermediate studies just as I finish up with WK. I’ve stuck to my turtle pace for a very solid year and a half now , and I’ve already outpaced several rabbits I’ve seen around the forum in that time , so I can confirm that if you stick to it, the slow and steady method does work.
How many daily lessons do you think you can handle? Think about what you’d be capable of doing on a day when it would be very hard to study, like if you’re sick or depressed or on vacation or getting married or whatever. That’s the pace you should be aiming for, not what you’re capable of doing on a good day.