As someone else said, check with your State regulators as they may be more stringent than the Feds. However, here is how I believe it should be handled.
1. You have a solid waste when the material is spent and must be reclaimed prior to reuse. If it is a solid waste, you must designate it and it will certainly designate as a Haz Waste due to ignitability.
2. You must now manage this haz waste under all the appropriate rules for your generator status including labeling, accumulation start date, storage locations, weekly inspections, and tracking of amounts generated and on hand, etc. until it is no longer a haz. waste.
3. If you distill the waste, once it is distilled, you can delete the recovered amount from your annual waste generation totals (this may be important for yoru P2 planning), and remove this much waste from your amount on hand for accumulation purposes. Of course, any still bottoms must be designated and will likely be a haz waste so they must be added into your waste generation and properly managed etc.
4. In Washington, it makes sense to distill the waste as soon as possible as they also give you a break on the generation status. For example if you work 20 days a month and generate 10 gallons of haz waste a day, in a month you have generated 200 gallons of haz waste and would exceed the lbs/month for a CESQG generator (100 gal * 8.34 lb/gal * .70 spg = approx 659 lbs). However, if you distill this every day, you only generate 10 gal of waste before it is recycled by distillation or approx. 66 lbs. You only have to count the maximum lbs generated prior to distillation for your generator status so in this case you would be a CESQG generator and not have to meet all the additional requirements for a SQG or LQG generator. Depending on the amounts of other haz waste you generate, this may be beneficial to you. Also, if you can set up a system so the distillation is continuous, (you distill the used acetone as soon as it is generated and the product is returned via hard piping to the virgin solvent tank), you can avoid ever calling this a haz waste. (apart from the still bottoms of course.)