It most definitely cannot with PPLNS and a 5xN reward. However people out there have all sorts of strategies they desperately invent to try and increase their profits. There are many threads scattered throughout this forum for people trying to change reward by altering hashrate at particular rates vs time, different addresses, different usernames, changing when to jump into and out of a pool, leaving during times of bad luck, or good luck or somewhere in between and planning to come back when X happens, renting expensive hash just to "keep their 5N high" etc... they're all futile. The only thing that matters is the total number of hashes you contribute, how much it cost you to contribute those, and how lucky the pool is at the time you contributed them. In the days of proportional reward system pools, there were plenty of ways to game the system. Luckily no bitcoin mining pool today uses such a system (except for newbies who appear out of nowhere and think they can create a pool with no experience, slap together whatever software they can find and announce it, thinking it will make them a fortune.)