Get your partner in, they are a “partner” in all of this. They will have hundreds of combined years doing this, they will have an understanding of your business and will be able to advise you, in detail, the best method for your business. I believe no one simply tests AX out of the box and goes live. What you need to remember is that this is just a tool. A bit shiny expensive tool, but a tool no less for you to wield for your benefit or detrement. Customers go through an implementation plan to get them to the stage of go live - Microsofts chosen methodology is “SureStep”. As for the slow migration over the course of a year this never happens, no one runs parallel anymore, if you have the staff to do this you are over staffed!. This leads to a middle ground. A remodelling of working practices, AX falling into line with these. Then there are workshops, modelling, delivery, training, user acceptance phases, all coupled with data migration, integration and reporting requirements. You get to the stage where all the changes are written and tested, all the users are trained and understand the system and all the reporting requirements are done. Then you go live. However that statement is a lie. No one gets to that stage. You need to be “happy” at the level you have got to, ensure it will not cripple the business, make a judgement call and then go live. Please be closer to the 90% than the 10% when making this step, but you will never be 100% happy. Also ensure at each stage you get the users/key users buy in and work in the feedback. Also get them to “sign off” on each stage - this is them saying “yes - we are going in the right direction” otherwise at live you will have the “I told you so” brigade, although they will be there as well. Stay calm, plan well, test, test, test and make sure you have a working relationship with your partner, the experience they bring to the table is valuable. There, my 2 cents! I can list horror stories, lovely go lives and everything in-between. I am the constant, the customer is the variable, and therefore the customer has the greater influence over the success or failure of the project (in my opinion).