Instead of having to purchase time, have it so you have to purchase a new character. This prevents alt spamming, unless they just wanna make a large donation and will allow players to not have to worry about whether or not they're going to be in combat with an animal and then get kicked out because their play time is up. Finally, it reinforces survival, as no one's going to take their characters life so casually when they have to pay to create another.
If everyone could post their opinions on this below it would be fantastic, thank you!