Giving 110% is only a smart idea for very short periods of time, or if its a life or death or serious harm scenario. You want to put in 110% if your life was on the line in a survival situation, you can even give 110% for a short period of the work day. If you try to give 110% for anything more then about 25% of the day you are going to end up injuring yourself or your body is going to quit on you from exhaustion in no time. Every company tells their employees to work at 110% because it means better profits, but what will end up happening is employee turnover and injuries are going to be so high that the company will wish they eased off the expatations a bit. A machine you can have run at 110% for a while, but they don't have minds to keep sane, they dont have countless parts that can break down and take a long time to repair, and they don't have many other tasks they need to perform once that particular job is done. Part timers work part time because they have other things they need to do or want to do the rest of the day. If they worked 110% the whole 4-5 hours then they can say goodbye to whatever plans they had for after the shift. Its even worse for full timers because they already have so little time and energy after their shift as it is. If this job involved something as important as saving human lives like a fireman or a doctor then I wouldnt see any issue with expecting 110% whenever possible, but delivering Suzie's new handbag that she bought on the Home Shopping Network isnt exactly a job worth giving 110% for from start to finish. Pay has nothing to do with it. If a preloader made $50 an hour they still should be working at the same level as if they made $2 an hour. You can't expect someone making $2 an hour to give 110%, and someone making $50 an hour to give 300%. The only time that higher pay should equal higher work effort is when its contractually agreed upon.
I can't stand the phrase "Just do your best", which is no different then saying "all you have to do is something as simple as the most you can possibly do". Your not going to convince me that the best that I can possibly do is somehow just barely acceptable. Its just a way of tricking workers into trying their hardest while feeling lucky that management somehow doesnt expect too much from them. Instead of saying "just do your best", a better phrase might be "just put a solid effort in"