By saying portulacas are annuals, does it mean they grow once a year, bear flowers and seeds, and die out in 12months time?
I have my portulaca all bearing beautiful flowers but the stems are starting to bend down mid-october and starting to look unhealthy, does this mean it cannot regain its previous strength?
An annual plant is one that has a short life-span. It grows, blooms, sets seed then dies all in one growing season. Annuals often bloom prolifically since they don't have to build big root systems or store energy to power next spring's leafing out. Portulaca self-sow so they don't always need to be replanted. They don't tolerate any frost and they like soil on the dry side and lots of sun. It might be that your portulaca have exhausted their potential. In frost free areas, it may live through the winter but won't provide a show again next year. If your portulaca are getting leggy, trim main stems back to a side one. Be sure to gather some seed! Here is an article on potential problems with moss rose. https://www.gardeningknowhow.com/ornamental/flowers/portulaca/no-flowers-on-portulaca-plant.htm