Google GCM: How many Sender class instances should I have

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http://stackoverflow.com – To send a PUSH notification to android device I should create a Sender class instance, than call it "send" method. After that this instance goes out of scope, and probably goes to GC. So, Can I create one instance of Sender class (put in some singleton for example), and use it later? May be some concurrency issues present here? Or is it better to create Sender instance on demand? (HowTos)