A newcomers three questions

Hi everyone- I am just joining you with 10 browns who have been laying an average of 10 eggs a day, usually a daily double yolker and an occassional triple yolker. They are kept in a large fenced area with some tree shade and a large coup- my questions are the following if anyone could help me-
1. They have eaten everything in the run and the ground is now a brown and sometimes muddy area with nothing except a dead tree to perch on- is this ok or should I add anything- I have no option in resiting the run?
2. How long do chickens live after their initial laying period - I will be keeping my to the end!!
3. They get fed layers pellets, some corn mix, household scrap and weeds. Sometimes they pass watery stools which you reference say may be due to underfeeding!! or too hot- I cannot see how either could apply - can it occur with too much greenery?
Plus sometimes I get 12 eggs a day for 10 hens- is this ok? Many thanks- Hattie

Hi - I am also fairly new to this and am keeping 11 hens in a fixed enclosure at the moment.  I have tried chipped bark - but there is a fairly lengthy discussion going on this forum about all this - see "using same piece of ground" , also there is a posting by I think 'Aunt Sally" which shows fabulous photos of all the sorts of poo your hens should and should not be doing.  I was pretty astounded to see what they routinely do - but it put my mind at ease re my own hens.  As for lifespan, not sure, I think several years although eg productivity declines after about 18 months with hybrids - anyway there are lots more people on the forum who can answer just about anything !