In Frostpunk 2, faction gatherings have many benefits. It provides players with a platform for communication and cooperation, and can promote resource sharing. During the meeting, you can discuss strategies together and enhance team cohesion. It can also stimulate new ideas, improve the efficiency of problem-solving, and allow players to better survive and develop in the world of ice and snow.
When a faction likes you enough or has enough enthusiasm for you, they may start holding rallies. As the rally continues or grows in enthusiasm, it may spread between different areas (often starting in residential areas).
When the rally begins, depending on how much the group likes you, you can request the following benefits:
Recruit more members of this faction
Extra calories earned
Or the third special action (depending on the group)
Be aware that sometimes rallies may increase tensions with opposing factions. For example, passionate propaganda by stalwarts may lead to negative relations with pilgrims. Some protests may further escalate tensions by actively trying to disrupt ongoing rallies.
If tensions between your groups have reached a breaking point, or you don't want to increase radicalization on either side, prolonged rallies are not always beneficial.
In addition to heightened tensions, longer gatherings may begin to skew the proportion of individuals in each group. Depending on how you want the game to play out, you may not want the rally faction's numbers to increase to the point of potential radicalization and dominance.
However, if you need the benefits of a rally, or to deal with tensions between opposing groups, you can extend the rally if a faction continues to have strong support for you. If their relationship leaves the gold zone and enters the neutral white zone, the rally will end.
It appears that if a rally expands, you can still reap the benefits of your first choice while enjoying the additional benefits of the expanded rally. Therefore, if you select "Hot Seal" for the first regional rally, and select "Recruit" for the expansion rally, you will see two benefits; additionally, if you select "Hot Seal" twice, you will enjoy double benefits.