This would be a perpetual subsidy - not one that runs out ?
Is there no competition to mine the most max POW transactions, and accrue the most mining subsidy ? A professional miner as you say in your paper.
The subsidy is perpetual, yes. There is no competition to mine a particular block; all miners can mine their own max difficulty blocks - they just have to be careful not to do so outside the path of most cumulative difficulty. Doing it like this maximises PoW efficiency, since no PoW is 'wasted' in orphans, it all adds to the security of the DAG.