Moving higher in the value chain means instead of you doing things that the client well understands the dimensions of, you are now doing something they don't understand the dimensions of. This is a critical and risky point. If you dive into implementation, they are going to be unhappy.
To serve them well, you have to now understand what they do not understand, and what is actually important to them. Almost certainly timeframe is important, but there will be a nuanced balance between 3 points of the triangle- time, features, cost- and you/they can only control two. The third is dependent on the others.
Upon eliciting more about what is actually important about the business context and opportunity, you help them most by presenting a strategy that incrementally and sufficiently delivers what is most important to them in the order of importance in the timeframe that matters.
Whether or not they know it, this is a strategic planning engagement first, before it is a implementation engagement.
And maybe you learn that cost is not an issue, they have critical needs in terms of features and time, so- you or they need to find additional resources and then manage them through implementation. Acting in a program management capacity over additional resources brings its own challenges, and it brings its own benefits. This is the transition from solo contracting to consulting. This profit margin on less expensive resources' time is how the money is made in consulting.
HTH.
However, is a 1 year timeframe something common / acceptable in the industry? I don't think everyone is hiring sub-contractors and it's rather hard for one person to deliver anything substantial in 1 year unless they work overtime like 50 - 60 hours per week.
So- in terms of having stuff that needs to be done that takes a year or more- yeah, every organization has those. Is it common for there to be one thing that one contractor works on all by themselves that spans a year- sure, less than it used to be, not uncommon, but it speaks to a certain tempo and/or oversight culture that one has to be careful about.
It would be useful for you to understand, from the higher level planning perspective the organization has- why would this be shaped and scheduled this way? Sometimes these things are little white elephant or skunkworks projects that an exec wants to get done but has to keep on the downlow...could be any number of things.
The reason to understand that stuff is because it kind of becomes a risk to you, because these kinds of unusually shaped things also get cancelled all the time, for all sorts of reasons. If you put all your eggs in this basket and then things change- whatever the language of your agreement, you're potentially left high and dry.
So- even if as you are discovering more and making plans and so forth and it all seems good, it's a year or more, makes sense for you alone to do it, etc- still, you want to break down the work into phases (project scoped units), and report on those phases and on the larger phase plan. What you don't want is someone 6 months in poking around being like- what the eff is this? 6 months delivering nothing? What are we doing here?