I don't remember ever having received a reminder. I'm pretty sure that Universal now operate the same way as Disney. However, they are currently offering a $70 discount for renewing your AP:
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Renew Now And Save $70!
Don't let that Annual Pass expire
renew your 2-Park Preferred Annual Pass now and lock in the special low renewal rate of $99.95 plus tax. You'll continue getting an entire year of fun and excitement for about the price of two single-day admissions, plus a Universe of special passholder benefits! Don't miss out on all the special events and exciting new attractions! Call 1-800-564-5764.
Regular price $169.95 plus tax.
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Not sure if this is a special offer, or the regular discount for renewing. My AP expires in May.
Also, in the Passholder section of their website (accessible by inputting information from your pass), it states that Online Renewal is 'Coming Soon'.