Yes getting sieged too soon might be a problem and getting sieged continuesly is too. There are several ways you can build up and never get sieged though.
1. like some said you can buy the protection for X hours, this might not be an option for the early player, but later on it will be easy to get the crowns for protection from questing alone.
2. You can send out cheap units into pvp as sacrificial lambs, they'll get slaughtered, might even survive to be used again and you get the attack protection after. Finish the fight fast by rushing your units towards the enemy to have more protection time. As some said protection time allready starts inside the fight, not after. This is especially easy playing orcs.
3. Let your town have close to 0 or 0 Battlestrength, this is especially easy as elf, because they use deers and forest wisps to create income. Also with humans and their lifestock?
4. Always have some gold to pay off.
So there is a lot of methods you can use to be secure early on. The problem is not the game itself, the problem is that the ingame "Help" library is not showing those options well enough. Give one of your mods some crowns or game copys for writing up guides and tips to be added ingame. Players will have alot more fun and mods will have alot less stress in the "Help" channel.