Some of you guys just don't get it.......it's not about a fear of free players catching up (news flash, you aren't. Quit dreaming). The trials don't contain the bonuses that top gem players have which is why their stats are astronomical. Everyone has a unit cap of 1500 (provided that you have 500 allies) so to keep pace you can't just get more units but you'd have to get the same bonuses which you can't get through trials.
The problem is the inability to get rid of hackers who can finish countless quests and build profiles that are impossible to defeat. Until the holes in the system are fixed it is a good idea to limit the amount of any strength impacting or war impacting item that you can possibly acquire over a short period of time. 1/day or 9/week is a perfectly reasonable ceiling IMO but that's up for debate. The bottom line is that there should be limits.
There was a time where players were able to farm cactus potions and we saw how that played out... It's a bad idea to give out health regen potions too for that matter but that's besides the point.
Limits are necessary to reduce the impact of exploits in the system.