I usually do not repot any plant, guava also, until the whole root ball is filled nicely with roots. Plants when repoted, first send strong roots that try to go as deep as they can, leading to roots showing tru the drainage holes shortly after repotting. That doesnt mean that the whole soil area has been occupied, and doesnt mean there is a need for a repot. I always take out of the pot and inspect how tight the roots have grown, if they are pretty netted i repot. Another clue that there is a need for a repot should be the soil drying too fast. The soil check obviously can be harder to do ,if your pot i very big awready.