Renovate or rebuild?

My wife and I just had old carpet in two rooms replaced with new hardwood-style flooring. We plan to do the same in at least two other areas of the house. We also plan to redo the 2.5 bathrooms at some point. Because most of our windows are missing storms and/or screens, we want new windows. We need new soffits, because ours are particleboard and showing rot in many places. The cedar siding may need replacement, too. It saw better days twenty years ago.
My question is this: At what point should one tear down and rebuild rather than keep putting money into expensive renovations? I’m not expecting an exact answer, but is there a percentage of a home’s value that one might use as a guideline? Or a percentage of the estimated cost to rebuild? For instance, if renovations will cost over, say, 60% of rebuilding? Any thoughts, ideas, or maxims regarding this would be appreciated.

Everything you have described is cosmetic - in relation to the basic underlying structure. If and when you start finding that the structure itself needs extensive repairs or alterations, then you need to have a professional appraisal and ask,
“Is this home worth remodeling!”

I don’t know where you live but in California there are big tax consequences. Remodels do not cause a reassessment of the property. Given the rise in California housing prices in the last 10 years this can mean a difference of ten to twenty thousand dollars a year in taxes. There are lots of more or less new houses with old garages or one wall from the original building for this reason.