Hi, I've did the LNAT last year, and would recommend two sites for shorter revision prep (Also, if you're finding it tiring, remember to take breaks! that is way more important than trying to cram in a few more questions/ tests).
Firstly, If they're still there, law mind had shorter 14 question tests although they're significantly easier than the actual LNAT and while it isn't LNAT prep, Khan Academy have a really, really good LSAT prep course where you can do 7ish (I think) questions at a time. It's a different format to the LNAT, but the skills are the same and its free and has a good interface where you can choose the difficulty and type of question! Both of these are free!
I hope this helps and good luck for when you do the LNAT!