LET - Names in Formulas - Generally Available

I suspect it will be a while before any widely accepted good practice is defined.  I wouldn't worry too much about defining sequences of variables within LET since they are strictly local and do not clutter up the workbook namespace.  I have adopted a number of practices that are not generally accepted but which work for me.  Where the formulas are of a mathematical nature, I tend to use elements of the Greek alphabet together with subscripts, an example of which is given below   

= LAMBDA(D,
    LAMBDA(xᵣ, tᵣ,
      LET(
        δx₁,  δt * D(xᵣ, tᵣ),
        δx₂,  δt * D(xᵣ + δx₁ / 2, tᵣ + δt / 2),
        δx₃,  δt * D(xᵣ + δx₂ / 2, tᵣ + δt / 2),
        δx₄,  δt * D(xᵣ + δx₃, tᵣ + δt),
        xᵣ₊₁, xᵣ + (δx₁ + 2 * δx₂ + 2 * δx₃ + δx₄) / 6,
        xᵣ₊₁
      )
    )
  )

 The steps δx₁,  δx₂, δx₃, δx₄ are successive refinements of a function x(t) corresponding to a step δt.  An advantage of using the subscript characters is that there is no risk of clashing with one of the 17 billion pre-defined cell references.

For business objects my names tend to be much longer such as 'openingAccountsReceivable'.  It is readability rather than conciseness that I value.