To be on the safe side, you'd better off using your h1b now as possible as you can. that way you can still keep dual status with AOS which won't expire as long as 485 pending. my philosophy is very simple: 2 is always better than 1. so keep your options open. Don't limit your choice yourself. 千万别自己给路堵死了,no kidding, life is not very sweet without freedom of choice, is it? 也别被公司的小恩小惠所迷惑而迷失方向。your goal is 尽快搞定绿卡,不是省几个小钱,弄清西瓜和芝麻噢。至于能否改回h1b, it depends on different company and its HR. no one can promise u anything in the future. think about this, do u have time to apply h1b after 485 deny? There will be a gap btw AOS and H1b then. 个人认为,太被动, too risky;但若你有h1b and AOS, 就机动多了,no matter what happens, like being laid off or company bankruptcy etc, you can go right ahead using EAD to work anywhere in US. 既便当时你没有EAD, not to worry. you can still take time to apply because your AOS is still valid. In a word, I always use my AOS (AP & EAD) as my backup. I have learnt all this the hard way in the past.
Hope it helps. 不妥之处,请各位不吝赐教。谢谢。