We adopted her at 6 months old, previous home wasn't the best and she was very timid/nervous at first. She settled nicely but interaction with us has always been on her terms and although she's really affectionate and loves cuddles, being picked up etc she would never voluntarily get on anyone's lap and wouldn't stay more than a minute if you put her there.
Then a few weeks ago she suddenly started getting on DH's lap (despite it taking her much longer to trust him than me) and settling for a while, properly lying down and going to sleep. I was pleased but also a bit put out because she still wouldn't get on my lap, only walk across it to get to DH which seemed very unfair when it's me that feeds her and cleans out her litter tray! So fairly typical cat behaviour, right? 
And then today she's clearly decided my lap is the place to be. She's come and curled up on me twice for about half an hour each time (when I was supposed to be doing stuff and about to get up, obviously) and I genuinely feel like I've won the lottery I'm so chuffed! She's almost 10 years old so it's taken long enough but I'm delighted she finally trusts us enough. Know changes in behaviour can indicate health issues so am keeping a close eye on her but she's eating well, toilet all fine, no hiding behaviour or anything so think she's just decided she's a lap cat after all, finally!