Hello,
do I understand it right - you pay a small amount of money per month and for this fee you have the right to use the latest version of PS ( or whatever product of Adobe's portfolio).
Some day, when you stop paying, your products refuse to work anymore, so there is no way to use your precious PSDs or layered TIF anymore ?
In opposite to this procedure - when you buy PS 'by the old way', you own the right to use this product for eternity, so you always have the chance to read and use your files.
Robert