IMS Bearing

Not by year. Many IMS bearings last a long time but some don't. A careful inspection of the engine oil and filter can provide clues. The 06 to 08 IMS bearings cannot be replaced unless you tear down the engine.

Mine is an 08 911 Carrera Cabriolet. Any other way of telling other than monitoring the oil? Such as by date of manufacture?

1999 to 2004 (M96) can be replaced without disassembly. 05 to 09 (M97) will require engine disassembly to service. replace with a LN, pretty cheap insurance to keep the car safe from failure (i've seen multiple first hand)

the LN bearing has to be repeated every 50K miles. better to go with an oil injection solution which is $3K but permanent

LN IMS Solution is a permanent fix

If you have a 2006 through 2008 model, it's recommended to have the grease seal pulled to allow the engine oil to lubricate the bearing. The failure rate is really low on these bearings, so taking this simple precaution should extend the life of your original bearing. 2000-2001 model years can have either the factory single or dual row bearing, so you have to verify which bearing you have before ordering a replacement. Late 2005 model years can have the non-serviceable bearing as well. If the engine was replaced, the engine will have whatever bearing was being used in that model year.