Sexeternity
Sexual intercourse with someone which will last forever, and ever, and ever, and ever...
...and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever, and ever...