How to Make Mounts Permanent
First, buy whichever mount you want. It doesn't matter if they are 1 day mounts or 7 day mounts. Now, if you get a 1 day mount simply exit to the character selection scene, then right click on your computer's clock (should be down in the right hand corner of your desktop). Select Adjust Time/Date and roll the days ahead by 2. If you choose a 7 day mount instead then simply do the same thing but roll the days ahead 9.
Go back and select the same character you were using and then click to begin playing. Check your mount in your inventory and you'll notice that the timer on it now reads all 0's. You can continue to use this mount forever and when the 2 or 9 days have passed you can even change your clock back to normal and your mount remains perpetual.