Do you have Aeroplan? If so... some questions

So, I was thinking of signing up, but I’m not sure if it would be worth it. Apparently it’s free, so I guess not much effort there, but for those of you that have this card, how often can you actually get a trip out of it? How many points do I earn per dollar spent or, in general, what is their conversion rate? And, do the points expire?

Thanks.