Yes, you should have valid ACS and IELTS at the time of invitation. However, because EOI remains in the pool for two years, the same may not pose issues to any such candidate. In certain cases where individuals took the skills assessment/IELTS before lodging the EOI, some problem can be there, particularly regarding the IELTS language results.
It is recommended to file the EOI as soon as the IELTS results are in hand. In case any decision is not made within the two years, the petition will not be considered a part of the EOI bank.
The ACS skills also expire after two years and in case you want to re-file, you will have to re-do the evaluation and submit a fresh EOI.