I know someone with grown-up DC (youngest is 21). They are all very capable individuals, establishing good careers of their own, and are also very likeable and kind.
However, they still require regular cash handouts from their parents, still rely on their parents to organise their car MOT/insurance/tax, still require their parents to sort out living arrangements if notice is served on tenancy, etc, still require their parents to organise Dr's appointments, still require mum or dad to deal with anything unpleasant out of their field of experience.
All well and good I suppose as long as their parents are around to do it, but what happens when they're not? Will they get caught driving a car without insurance and losing their licence/getting a criminal record? Will they find themselves homeless? Will they find themselves with debt collectors on the doorstep?
they may be capable of doing everything their parents do for them, but unless they see it as their own responsibility and have the mindset of remembering that it must be done, chances are that they'll have slip up before it becomes a priority in their minds.
One of the grown-up DCs now has a summons to court for ignoring a speeding fine. She left home, mum and dad changed her address, she got caught for speeding, got sent a letter and ignored it because she has never had to experience unpleasant consequences for not doing something. Had she learned this lesson earlier with consequences that didn't carry quite as much significance, maybe this could all have been avoided.
Do you want that for your DC OP?