Mine was roots from a hedge. I got rid of the hedge.

There are so many variables from one home to another that the only way of knowing is inspecting the line. Are you willing and able to dig up a portion of line? ( It's normally only a few feet of pipe that's bad). How old is line? ( Most is good for decades). What kind of material is line made of? ( Some is easier to repair than others). And a few more if you have answers to those.

I appreciate the input.

I live in WeHo, California and it's illegal to cut down trees as most are city-owned. Plus my neighborhood is full of hedges, hard to know where one begins and another ends:(

My plumber showed me video camera evidence and it looks like the drains were full of roots. He said that roots grow in pipe cracks and it's pretty damaged. He offered a biannual pressure jet-stream service in lieu of replacement, but said the pipes could burst because of the cracks. It's the main line sewage that's primarily affected. He said replacement is cheaper than repair because they are so old.

There are no silver bullets for that.

I too had tree roots and had the line from the house to the septic tank replaced. No more problems.

Thanks all, guess I'll have to bite the (non silver) bullet:(

Look into pipe lining, they clean out the drain line, then epoxy a new lining inside the existing pipe, taking care of any cracks.

Thanks, he said that would be more costly and less durable:(

That's because he doesn't know how to do it. Get a quote from someone that knows how. It is just as durable as new.