The slight bit of excess cage travel (versus the 7s cog spacing) accumulates as the chain is shifted away from the center (4th) cog, but with the hi and lo limit screws enforcing correct indexing at both ends of the cog stack.
The only issue then, if the indexing error isn't noticeable, would be that the derailer will be coming into very firm contact with the lo-limit screw each time that the cable is trying to move the chain to the largest cog.
Over time, such setups have been known to cause the lowest-gear detent inside of the shift lever to wear out, due to the cable tugging cyclicly against the detent with every rotation of the cranks. Note that the problem only surfaces after the shift lever is used with a correct rear derailer, where the detent (and not so much the limit screw) is having to establish the low gear indexing position. I have twice bought indexing levers with such wear on the low-gear detent position, and I'm pretty sure that I know how it was caused.
In the related case of STI shifters, where the detents don't yield (and don't wear), typically it's the cable that fails prematurely when a "tight" adjustment to the lo-limit screw causes over-tension of the cable.
For limited "hours" of use however, none of the above should matter!