Some, not all, species of bamboo display gregarious flowering. Others flower sporadically, but still at long intervals. A gregarious flowering can spread over several years, for example in the case of the recent gregarious flowering of Fargesia nitida, it didn't apply to all cultivars and has stretched over at least 5 years. The flowering interval of bamboos varies from species to species, and some types of bamboo have never been observed to flower even though we have had them under observation for over 100 years in some such cases. The "48-50" number you quote probably applies to that specific species in NE India that results in rodent plagues, and I would tend to suspect the number is spuriously precise: we probably only have a handful of observations. For the types generally in cultivation in cooler countries, my guess is that 50 years would be on the low side.

Stress can result in flowering of specific bamboo plants, or parts of specific plants, but this does not trigger a gregarious flowering. Merely being in the same garden as other bamboo does not result in stress, otherwise the botanical collections would be stuffed. But I can imagine growing bamboos very close to each other so they compete for water and nutrients could be stressful.