All great responses.....thank your for taking your time to do so.
So, as I look back at my original post I see a couple of details I left out, that along with some of the comments/questions above I will address here below
1. I currently have a house with a 16x22 bonus room upstairs. I have a layout now I have been building for 13 years. It is substantially complete save some scenery work I would do. So I there is no more room to grow. I have several Lionel 21" cars....and yes it is very tight (I have o72 min. curves) but I like them. So that is what generates the question. I agree it very nice to go upstairs when it is cold (although I am in Florida) raining or in pajamas to work on trains for 10 minutes or 2 hours....doesn't matter.
2. However, this would be like the dream layout - I would go to minimum of 20/25 x 30/35. I would have a great place to actually run 21" passenger cars. The tradeoff is accessibility for size. Is it worth it?
I think that a trip like that to your layout would get old in a hurray.
Mark's comment gets right to the point of what I am trying to determine.
3. I am going to buy some acreage...20-30acres +/- it is timber land/farm land. That has pretty much been decided. Investment etc...reasons that all would be another forum discussion.
4. I am 58 recently empty nester have kids are in college...so there is that transition.....plan to work another 9 years +/-
5. Not ready to sell the current house. But this land could certainly be a homesite in 5 years +/- I understand all the financial aspect of two properties, investments etc. Been in banking 31 years.
6. The building if sold one day, would be great for tractors, ATV, fishing gear, workshop etc etc. if the next one did not have a train hobby. So value would still be there if I never built a house. Next guy would have great home site with building to put whatever in.
7. Still researching cost of the building - that will certainly play a factor in the whole plan.
8 So I guess the bottom line question is ....Is it worth giving up convenience to effectively triple the size of the layout? Again realizing everyone has a different answer to that question.
thanks for all the feedback...enjoying the conversation.