I would hope that most of us are embedding peer assessment in our lessons. There are problems, of course - it means you are not only teaching the students content, but also higher order evaluative skills. This is great for high ability or older students, but it means a lot of scaffolding for students who are less able. Peer assessment for younger or less able students can be a time suck and unless it is done well it can be of limited value to the students. Either way it is unlikely to be saving you any serious time.
So, think vertically! Here's an example from KS4, but this works well at all levels. A lot of GCSE specs are taught over two years, which means you have two groups working through the exam units - one learning for the first time and the other revising. Get your year 11s marking the year 10 work, which will reinforce their understanding of the mark scheme. When they are done marking, they can create study guides or resources to help out their little year 10 buddy, and report back to you on general strengths and weaknesses. Not sure their marking will be as effective as yours? Teach them to moderate, and make sure each year 10 paper passes under the eyes of at least a handful of year 11s. What they lack in skill and experience they make up for in focus and ability to spend lots of time on each piece of work. Leverage the heck out of that!
Result? Year 10s get quality feedback and personalised resources and year 11 engage with the mark scheme in detail and consolidate their learning by teaching others. Best of all, you have twenty-five new, effectively deployed teaching assistants!
Never forget what the students can offer to the learning experience (not just their own, but their peers) and what you can offer. Then delegate, delegate, delegate! Get the kids to do the heavy lifting, at least where and when it is beneficial to them.