Since your seams are enclosed in the quilt you should not have any issues with your fabric unraveling, I have used as small as 1/8" seam just making sure my stitches are a little closer together and have not had any issues. My quilts get washed a lot - the one on my bed at least everyother week and it has been 12 years. Keep saying I will make another one for me - but haven't gotten there yet.
There are a lot of antique quillts still in good shape. Those that aren't we have to think about how they were made: hand stitched which is not nearly as small and stable as machine stitching. Fabric dyes back then were more caustic causing some deterioration of fabric (some colors more so than others). We also don't know how much those were used and under what circumstances. I know a lot of the more elaborate ones were saved for special occasions but a lot were used daily under much more severe circumstances than ours will ever be used.
Personally I believe that if you use quality materials, have a good stitch length your quilts will last longer than you will