Personally I use my diapers for a genuine medical condition, and therefore feel about as old as a 41-42 year adult can be
however when I am in diapers/nappies in the privacy of my own bedroom, or hotel room if I am around I tend to regress to the stage I was when I was 12-18 months old as that's the time when I felt the most loved & cared for and one thats still very dear to my heart.
And one that I frequently go back to as I didn't have a great childhood due to bullying as in bring a victim of abuse and torture, and whilst thankfully not from my family it left its mark in the form of ptsd and depression for which I have been trying to recover from for decades, see my previous replies if you haven't already done so.
However right now while writing this I am pair of in tena value adult sized disposable diapers which really resembles the old pampers baby-dry lotion care ones from the 1980's and early 90's, as they have lotion in them that is very soothing and relaxing.
And I couldn't be more happy to be in nappies even if it makes me look & feel like an over-grown toddler, so be it, as specially given as I dont have to worry about the outside world and this is a great feeling of self isolation not because I am sick or anything I dont have covid-19 as I tested myself last week.
I just cant be bothered to get out of bed st this time because of two reasons one I dont want anyone to see that I am in diapers for obvious reasons, and two because I feel in a protective bubble like a child and I dont want to burst that feeling.
I hope this helps awnser your questions.