I’d say hang in there until at least 24 months. It takes 12 months to bring most incremental products to market, 18-24months plus to bring anything really innovative with R&D, so I wouldn’t expect you to really have much production work in your portfolio yet.
Keep in mind you only get to quit a job once, so ask yourself have you learned everything you can from your current company? Before I left I’d want to know why they are taking you off projects? Is there a perceived problem with your work or your process? If so is there anything you can learn from the feedback they might be able to offer you?
In the past 20 years I’ve only had 4 employers. I’m not saying not to leave, but make sure you are selecting your next move carefully and not just running away from something.