  We have investigated the title question for the W4-08 thermochemical
benchmark using partial-wave truncations of a large reference (REF) basis set,
as well as for standard F12-optimized basis sets. With the REF basis set, the
root mean square (RMS) contribution of i functions to the total atomization
energies (TAEs) is about 0.01 kcal/mol, the largest individual contributions
being 0.04 kcal/mol for \ce{P2} and \ce{P4}. However, even for these cases,
basis set extrapolation from \{g,h\} basis sets adequately addresses the
problem. Using basis sets insufficiently saturated in the $spdfgh$ angular
momenta may lead to exaggerated $i$ function contributions. For extrapolation
from $spdfg$ and $spdfgh$ basis sets, basis set convergence appears to be quite
close to the theoretical asymptotic $\propto L^{-7}$ behavior. We hence
conclude that $h$ functions are sufficient even for highly demanding F12
applications. With one-parameter extrapolation, $spdf$ and $spdfg$ basis sets
are adequate, with aug-cc-pV\{T,Q\}Z-F12 yielding RMSD=0.03 kcal/mol. A limited
exploration of CCSD(F12*) and CCSD-F12b suggests our conclusions are applicable
to higher-level F12 methods as well.
