I’m studying Chinese mostly to read and speak, but I spend the majority of my Skritter time practicing writing. I typically have 150-plus reviews a day, the majority of which are writing — and writing takes longer than definition. But if I switch to definition only, will I build a huge backlog of writing in the event that I later wish to restart writing reviews? What do you all do?
If you don’t study writing, you will build a backlog of some kind. This is not necessarily related to Skritter, it’s just how our brains work; if we don’t study something, we will not learn it or retain it if we have learnt it before! 
Being able to read something doesn’t mean that you’re able to write it.
If you focus on reading for a while and cut down on writing, you should expect to have to spend a significant amount of time catching up with writing if you wish to do so later. There is no way around this, and it’s, like I said, unrelated to Skritter. However, I don’t think that needs to be a problem. If you want to focus more on reading and speaking for now, cutting down on writing is a good choice!
Personally, I would select a subset of the characters you know and keep writing those. For example, you could keep the HSK 3.0 handwriting decks, but skip writing on anything else. How many of these decks you keep handwriting for depends on your level, of course.
There are two ways you can do this in Skritter. First, you can disable writing cards globally for your account, which means you won’t do any writing at all. This also means that no new writing cards will be created when you learn new words. You can still add these later if you want by relearning or rejuvenating decks.
Second, you can, when you start a study session, select which decks to review and which types of cards to review for those decks. For example, you could always uncheck the box next to writing for most decks, except the HSK 3.0 writing decks (as per my recommendation above). This means you still have writing cards that will come due for all other decks, but you can just ignore them.
Both approaches have downsides. The first doesn’t allow you to select writing for specific decks, and the second leaves you with due cards that you’re not supposed to study (which is not a practical problem, but might look/feel off). Hopefully, we’ll be able to deal with this more gracefully in future versions of Skritter!