You can use
http://www.liskware.com/ to check how many LSK you'll will get approximately (if you get an error-message like "application error" try to reload the site). With 100 LSK you should currently get around 1 LSK per month.
Thanks!
I was on that website. At first I thought this website is broken. There was a lack of patience just when it was needed. Loading takes ~ 1 minute.