If you go on the Nectar site or the app there's regularly double points offers on your next x (6, 8 or 10, depending on how often you shop) swipes with 100 bonus points on your final swipe.
I've also got life and home insurance with them which triples my points all year. Plus gives points for getting them (£75 of points for life and £25 for home).
There's often triple points codes given out both with online shopping and in store.
And if you have a delivery pass you get given 1000 points every now and then just because.
I started 2017 with £10 in points and I've spent around £100 and have just over £80 left (that's without the bonus points for the insurance as they won't be paid until next year).
I use them to pay for my extra Christmas food with them. And double up for booze!
It does pay to shop with Sainsbury's all year, and I don't find them that much dearer than somewhere else.