How much of a long term commitment are coverage groups?

I'm pawing at the glass to get into IB from B4 but my B4 experience causes the thought of doing O&G make me feel physically ill. Ultimately I'm curious if joining a coverage group locks you in to that sector long-term or if moving to something that seems more interesting like RX (Based on pure vibes, I have no real evidence-based reason to assume this is more interesting) fairly unlikely. I am so ardently against doing O&G it's the only coverage group I would consider declining an offer for and staying in B4, but if it's fairly easy to jump around maybe it's not a big deal.