I am doing a survey of Savo Finnish books in Finnish libraries.
For how long do you keep the loan records of your books?
Do you mean to inquire for how long do Finnish libraries have information on borrowers of a book after the book has been returned? In Helsinki region, we do not keep such loan records at all. Instead, the customer can him/herself see his/her own personal borrowing history in his own record in our database Helmet (http://www.helmet.fi/). For that you must have pin code on your HelMet card.
If, instead, you mean lending statistics of a book: we keep count permanently and the cumulating loan issue number increases (hopefully) or at least stays (not so hopefully) up to the book is discarded.
With “Savo Finnish books”, do you mean books written in Savo dialect? In that case you may be interested in the list of fiction books in Savo dialect in HelMet libraries: http://www.helmet.fi/search*fin/?searchtype=X&searcharg=savolaismurteet…
There are many more, but they have not been indexed with a subject heading, unfortunately. In the National Library database Fennica it is not possible to limit the search to fiction, and include ALL fiction, so here are all the titles that come when you search with the subject heading that means Savo dialects (savolaismurteet): https://fennica.linneanet.fi/cgi-bin/Pwebrecon.cgi?Search_Arg=savolaism…