If factors like straining activities, constipation etc persist, then they enlarge faster.
Surgery is the treatment opted
for when the size is large and
hernia is symptomatic. Having said that, I would also say that the earlier it is repaired, the better it is. There are belts available for umbilical and paraumbilical hernias which you can wear to minimize pressure on the hernia.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!