I’ve gone through many emotions reading this thread from ‘omg think of the house you could get in Kent for 2,500 a month’ to I would have killed to be in central London at their age, to something in between.
I always lived very close by in Kent and it was always a ballache having to leave at 11.20 to get the last train when my friends could leave at 1am and still go to work the next day.
I ended up living there til I was 37 then moved hundreds of miles away, and I do think that having a pretty hedonistic lifestyle for 20+ years meant I ‘got it out of my system’, almost fully. Loads of my friends still live there but I no longer get pangs of jealousy at the gigs, parties and exhibitions I can’t go to. We have a lovely big house with countryside views, little stress, and that’s the pace of life I like now (I am 47). These days I value a lovely home, savings and nice holidays over regular nights out.
I do sometimes miss the restaurants, but we are about to move to another countryside location near a thriving market town, and that will fix that.
That said, they could still afford to rent on the outskirts, have a thriving social life and get taxis all the way home on that income, if they want to to. They are unlikely to get someone reliable to feed their dog outside of London though. In the City there are so many folks providing this service that you can dump them if they are rubbish, absolutely not so outside.
I think the best thing they could do is lower their rent by looking at zones 3-4. Somewhere leafy yet affordable. I keep hearing Walthamstow is good these days. Living in Z1 is crazy with their potential income, if they make the right move to a lower costing area, they could be absolutely minted and pay a mortgage off in their 40s.
As @Startuplife said, Londoners won’t come to see them - in my experience - if it involves a train and not the tube/bus. 45 mins and two tube lines, fine. 1 hour and no tube, very very bad. I could count on one hand the number of London visitors I had over decades. I can’t say I blame them. They are always unreliable and bus replacement services are frequent and a PITA.