Every client you meet will want to be your no 1 priority. Obviously, this is impossible, so you should carefully evaluate what you’re offering and select only as much time as you need to complete the work. Depending on what you’re offering, you can set a minimum delivery time of 2 days to give yourself some wiggle room for when you’re sick or just having a really bad day.
You can also choose whether or not you’re going to offer extra-fast delivery for an extra fee. I recommend that you do because you can set it to any time you like. For example, standard delivery of two days, extra fast in one day. Or, standard delivery four days, extra fast two days, etc.
Of course, don’t forget that delivery time will factor into your internal Fiverr search ranking, too. If you want your gig to be ranked high among all sellers by the level of quality as judged by Fiverr’s ranking algorithm, then you should strive to deliver as fast as reasonably possible.
Yes, positive reviews are important, but believe it or not, what I’ve seen is that Fiverr’s ranking algorithm values speed of delivery more than the quality of reviews. There are sellers in my category who regularly collect negative reviews, but they’re still ranked higher than other sellers because they deliver faster. There are also sellers in my category who’ve been on Fiverr longer than I have, but I’ve outranked them because they don’t deliver as fast as I do.
Fiverr loves fast delivery. Granted, fast delivery won’t undo negative reviews and if your work just sucks then nothing will fix that, but it counts for an awful lot.