Even some people sign up for 5 shells or more I'll be surprised actually complete 5 shells.(at least in a reasonnable time) People could iniatially sign up for say 3 shells, and then later on when they have actually completed a shell or two they could sign up again for more.
IMHO there is no emergency in having the shells reserved as soon as possible. The Age will evolve over the next months.. we can take our time.
Robert has a point too. I see Besharen has taken 3 shells that are placed next to each other, that looks like a good idea.