Well, I'm sure not the customer service, buddy, but I can tell you that I have been subscribed many times too and the tickets are a one time deal. There's only one exception I know, sometime ago, when they made major changes to the website, they did reset the counters and the subscription gave the welcome bonus again for the same period of time.
You're right saying that is not clear or really specified that this bonus will only happen one time, but if you look in the pic, it says "welcome bonus" and that tells the tale, at least Totem believes that.
Now, some fellows here say that you can score the tickets again if you take the subs switching every time the duration of those. I dunno, I always take the subs for the same period of time.
And well, if they own you tickets cause you score them every single single time, they also own me a few then. But, in my experience, is not that way.
Rex also just said that the Customer Service is actually alive and working despite the message that says that it isn't, so it will be worth to ask them to clarify the issue.