I got my horse on full loan last October, his owner cried her eyes out when I picked him up as didn't want to get rid of him but had no choice..she said she would be down in four weeks to check everything is ok & that was 15 months ago!! Never seen her again! But if she asked me I would be happy for her to come whenever but would want her to let me know she was coming first..
I've always written in into contract in the past to be able to visit pony at any time, tho where possible I would contact the loaner 1st.
Over the 1st 3 months I would visit every fortnight. Then monthly.
Had one livery in my yard for almost 5 yrs who had an elderly horse on loan - owner visited her at my yard 2 weeks after horse arrived - not been heard of since, and no contact for past 2 years and has moved house without giving the woman who is loaning the horse, her address or new details!!
When I had my big mare out on loan I wrote into the contract that I could drop by unannounced at reasonable times. I used to pop in every 2/3 weeks or so for a few minutes as I practically drove past the yard regularly. They bought her from me eventually and I still see them (not the horse though) at local shows, and they happily tell me how she is getting on.
My partners horse is a loan and we've had him 2 years now; he came to us on permanent lifetime loan as his owner had just got divorced, moved on with new partner and given up horses.
We keep in touch via e-mail/photos and the odd text. Owner is free to come over anytime but in the time we've had him, has only been twice, once to see where he would be kept etc (which is at home) and then Christmas just gone they came over with some carrots and polos
I've loaned out previously, my ex-eventing mare to a quieter life and home was fantastic; I was free and welcome to visit anytime but to be honest, only used to a couple of times a year as the home/rider was brilliant, anything amiss etc and she would text/call me so I had no reason to worry.
I think its reasonable to be able to go anytime (announced or otherwise) and if you're happy with how things are there shouldn't be any problem.
My gelding is out on loan to a good friend of mine who I trust to take good care of him but I still like to check on him when I can. I'm at uni so can't visit as often as I'd like but whenever I'm home- roughly every month- I drive past to check on him. I only officially visit him twice or three times a year, with her present. By driving past I get peace of mind that he is well and I don't have to intrude too much- I like to let her think of him as hers for the duration. However if she wasn't a good friend I would be inclined to visit officially more often. Generally speaking it's as often as you want it to be/feel comfortable to be- it's your horse at the end of the day and a good loaner should be happy with whatever suits you.
I had it written into the contract that I can visit anytime without notice during daylight hours and that the yard owner must be aware and agreeable to this so that was covered. Still not sure about just turning up though!