Sorry this is long!
We did similar pre-covid when DH and I worked abroad part of each year and often travelled. 11mths was the longest we were away but it was mainly for 4mth stints. We have a 2 bed flat with roof terrace between zone 1-2, and somewhere separate to securely store private documents/clothes etc. We had a buy to let mortgage on it anyways, but this and insurance is something you'd need to look into.
-We had a company manage it through AirBNB. They did the listing, organised cleaning, linen etc. At that time, they only took on properties within zone 1 or 2. We vetted 4 companies before choosing that one.
-We paid a higher fee percentage to have a meet/greet service. The 2nd time we rented it out though, they said that if guests arrive after say 11pm, they leave the key at a local convenience store that have key locks. The 3rd time we rented it, it turned out that they no longer did meet/greet and ALL guests had to collect keys from the convenience store. This would be ok because there was a shop underneath, BUT, that shop didn't have a key holding service and the nearest shop that did, was a 25min round trip to walk too. If I was a guest with luggage/family etc, this would be the last thing I'd want to do potentially in the dark in central London! IF you could attach a key lock thing on/near your property, I suppose that could work.
-The longer we had the booking calendar open, the more likely we were to get bookings, but even at its best, occupancy only averaged about 50%.
-The company were supposed to flux the price depending if it was a bank holiday, Christmas, major event nearby etc. They cocked up one time and someone had very cheap week over Christmas/NYE. I suspect they rented it to a 'friend' or themselves, but have no proof.
-Overall we only had a cheap blanket stolen, hair dryer and some air plants
-Initially, the company were fairly small. We'd leave a locked cupboard full of toilet paper, kitchen roll, bin bags etc and the cleaner would replenish using those. As the company expanded, they then wanted £20 a month for such incidentals. I felt this was ridiculous, especially when some months, it might have only been rented for 2 nights!
-Occasionally, we'd fly back for a weekend and stay in our flat. Initially, this was easy and no bother. As the company expanded, this too came with additional fees and rules.
-We knew our neighbours well and they contacted us twice about noise.
-During the time, London bought in a 3mth rule for short term lets. From memory this was booked nights, so if we only had it booked for 2 weeks over a 3mth period, then that was only 2 weeks worth of booking.
-After this change, the management company wanted to also list our flat on booking.com and other platforms. I wasn't keen that those sites have no reviews of the actual guest, plus, I felt they wanted to do this to try to cover up renting more than 3mths in a year. We stopped it all together because it had just changed so much from the 1st time we'd rented it out.
-The last time we went away, pre covid, we had a family friend stay for 3mths. She was in her 50's ex police woman and now a solicitor. Unknown to us, she let her 18yr old son stay in our flat. He has parties, broke things, smashed a hole through the wall plaster and it was left an absolute mess.
I wouldn't do AirBNB/management company again and very unlikely to rent to a 'friend'. Is your place near a hospital/uni/corporate company where staff might want year long rents or shorter rents? This likely isn't helpful at all OP, but happy to answer any questions.