It's common, but in my view unwise, to have these conversations without acknowledging that the answers vary enormously with one's wealth, social class, and income. Your search for a cutoff is missing a variable. How rich (or broke) do you expect to be over those 25 years. And how sure are you? (aka "How much economic confidence do you have?")
This is a real factor, and personally "How sure are you" is a real question. 10 years ago I was single with plenty of time and no money. I did pretty much everything myself (or at least tried). I didn't have the money anyway, but also enjoy the feeling of independence. I now am married with two children and a corporate job that I never thought I would have. I am not wealthy by any means, but these days there are plenty of jobs that would be more economical to pay someone else. I still try to do much on my own, but have begun to start hiring out some of the "businesses I don't want to be in." However, the #1 business I do not want to be in is my day job. This brings me to a point of confliction when it comes saving/hoarding. I do not want to work this job (or anything like it) forever. Although I have purged more/saved less lately, there is a certain part of me that thinks about it in the "make hay while the sun shines" type of mentality. Should I buy an extra one now while I can afford it? Now I have a stash instead of cash. But there is only a difference if it is something I am not sure I will need/use, right? Otherwise, essentially, I am buying "stuff" futures at a reduced price compared to the cost at the time I will need it later on. This is probably just me trying to justify my saving desires.
The flip side of "opportunity cost" is the space lost to your stashes of "handy even if I never use it" and "round-to-it" stuff. It can turn into: a workbench that is now only a shelf, scraping ice of your car parked out in front of the garage, and time lost moving things in and out of your own way just to find other things that you were sure you had... going to the store to buy a duplicate of a lost thing.
Then the reminder of reality. The "space lost" thing is no joke either. It was great all summer with easy access to outbuildings, outside storage, etc. Winter has hit in NH and I am completely snowed in, piled on top or myself, and in my own way. I would be embarrassed to count the number of things I have an "extra" of because I went and bought one because I could not find/get to the one I already had.
